Package org.python.core

## Class PyDictionary

- java.lang.Object
- - org.python.core.PyObject
  - - org.python.core.AbstractDict
    - - org.python.core.PyDictionary

- All Implemented Interfaces:
    `java.io.Serializable`, `java.util.concurrent.ConcurrentMap`, `java.util.Map`, `Traverseproc`
  Direct Known Subclasses:
    `PyDefaultDict`, `PyDictionaryDerived`

      public class PyDictionary
      extends AbstractDict
      implements java.util.concurrent.ConcurrentMap, Traverseproc

  A builtin python dictionary.
  See Also:
    Serialized Form

- - ### Nested Class Summary

    - ### Nested classes/interfaces inherited from class org.python.core.PyObject

      `PyObject.ConversionException`

    - ### Nested classes/interfaces inherited from interface java.util.Map

      `java.util.Map.Entry<K extends java.lang.Object,​V extends java.lang.Object>`

  - ### Field Summary

    Fields
    Modifier and Type | Field | Description
    --- | --- | ---
    `static PyType` | `TYPE` |

    - ### Fields inherited from class org.python.core.PyObject

      `gcMonitorGlobal`

  - ### Constructor Summary

    Constructors
    Constructor | Description
    --- | ---
    `PyDictionary()` | Create an empty dictionary.
    `PyDictionary​(java.util.concurrent.ConcurrentMap<PyObject,​PyObject> backingMap, boolean useBackingMap)` |
    `PyDictionary​(java.util.Map<PyObject,​PyObject> map)` | Create a new dictionary which is based on given map.
    `PyDictionary​(PyObject[] elements)` | Create a new dictionary with the element as content.
    `PyDictionary​(PyType type)` | For derived types
    `PyDictionary​(PyType type, int capacity)` | Create a dictionary of type with the specified initial capacity.
    `PyDictionary​(PyType type, java.util.concurrent.ConcurrentMap<PyObject,​PyObject> backingMap, boolean useBackingMap)` |
    `PyDictionary​(PyType type, java.util.Map<PyObject,​PyObject> map)` | Create a new dictionary which is populated with entries the given map.

  - ### Method Summary

    All Methods Static Methods Instance Methods Concrete Methods
    Modifier and Type | Method | Description
    --- | --- | ---
    `int` | `__cmp__​(PyObject otherObj)` | Equivalent to the standard Python __cmp__ method.
    `boolean` | `__contains__​(PyObject o)` | Equivalent to the standard Python __contains__ method.
    `void` | `__delitem__​(PyObject key)` | Equivalent to the standard Python __delitem__ method.
    `PyObject` | `__eq__​(PyObject otherObj)` | Equivalent to the standard Python __eq__ method.
    `PyObject` | `__finditem__​(int index)` | A variant of the __finditem__ method which accepts a primitive `int` as the key.
    `PyObject` | `__finditem__​(PyObject key)` | Very similar to the standard Python __getitem__ method.
    `PyObject` | `__iter__()` | Return an iterator that is used to iterate the element of this sequence.
    `int` | `__len__()` | Equivalent to the standard Python __len__ method.
    `PyObject` | `__ne__​(PyObject otherObj)` | Equivalent to the standard Python __ne__ method.
    `boolean` | `__nonzero__()` | Equivalent to the standard Python __nonzero__ method.
    `void` | `__setitem__​(PyObject key, PyObject value)` | Equivalent to the standard Python __setitem__ method.
    `void` | `clear()` | Remove all items from the dictionary.
    `boolean` | `containsKey​(java.lang.Object key)` |
    `boolean` | `containsValue​(java.lang.Object value)` |
    `PyDictionary` | `copy()` | Return a shallow copy of the dictionary.
    `java.util.Set` | `entrySet()` |
    `boolean` | `equals​(java.lang.Object obj)` | Should almost never be overridden.
    `static PyObject` | `fromkeys​(PyObject keys)` |
    `static PyObject` | `fromkeys​(PyObject keys, PyObject value)` |
    `java.lang.Object` | `get​(java.lang.Object key)` |
    `PyObject` | `get​(PyObject key)` | Return this[key] if the key exists in the mapping, None is returned otherwise.
    `PyObject` | `get​(PyObject key, PyObject defaultObj)` | Return this[key] if the key exists in the mapping, defaultObj is returned otherwise.
    `java.util.concurrent.ConcurrentMap<PyObject,​PyObject>` | `getMap()` |
    `boolean` | `has_key​(PyObject key)` | Return true if the key exist in the dictionary.
    `int` | `hashCode()` |
    `boolean` | `isEmpty()` |
    `boolean` | `isMappingType()` |
    `boolean` | `isSequenceType()` |
    `PyList` | `items()` | Return a copy of the dictionary's list of (key, value) tuple pairs.
    `PyObject` | `iteritems()` | Returns an iterator over (key, value) pairs.
    `PyObject` | `iterkeys()` | Returns an iterator over the dictionary's keys.
    `PyObject` | `itervalues()` | Returns an iterator over the dictionary's values.
    `PyList` | `keys()` | Return a copy of the dictionary's list of keys.
    `java.util.Set` | `keySet()` |
    `void` | `merge​(PyObject other, boolean override)` | Merge another PyObject that supports keys() with this dict.
    `void` | `mergeFromKeys​(PyObject other, PyObject keys, boolean override)` | Merge another PyObject via its keys() method
    `void` | `mergeFromSeq​(PyObject other, boolean override)` | Merge any iterable object producing iterable objects of length 2 into this dict.
    `PyObject` | `pop​(PyObject key)` | Return a value based on key from the dictionary.
    `PyObject` | `pop​(PyObject key, PyObject defaultValue)` | Return a value based on key from the dictionary or default if that key is not found.
    `PyObject` | `popitem()` | Return a random (key, value) tuple pair and remove the pair from the dictionary.
    `java.lang.Object` | `put​(java.lang.Object key, java.lang.Object value)` |
    `void` | `putAll​(java.util.Map map)` |
    `java.lang.Object` | `putIfAbsent​(java.lang.Object key, java.lang.Object value)` |
    `java.util.Set<PyObject>` | `pyKeySet()` |
    `boolean` | `refersDirectlyTo​(PyObject ob)` | Optional operation.
    `java.lang.Object` | `remove​(java.lang.Object key)` |
    `boolean` | `remove​(java.lang.Object key, java.lang.Object value)` |
    `java.lang.Object` | `replace​(java.lang.Object key, java.lang.Object value)` |
    `boolean` | `replace​(java.lang.Object key, java.lang.Object oldValue, java.lang.Object newValue)` |
    `PyObject` | `setdefault​(PyObject key)` | Return this[key] if the key exist, otherwise insert key with a None value and return None.
    `PyObject` | `setdefault​(PyObject key, PyObject failobj)` | Return this[key] if the key exist, otherwise insert key with the value of failobj and return failobj
    `int` | `size()` |
    `java.lang.String` | `toString()` |
    `int` | `traverse​(Visitproc visit, java.lang.Object arg)` | Traverses all directly contained `PyObject`s.
    `void` | `update​(PyObject other)` | Insert all the key:value pairs from `d` into this dictionary.
    `void` | `updateCommon​(PyObject[] args, java.lang.String[] keywords, java.lang.String methName)` |
    `java.util.Collection` | `values()` |
    `PyObject` | `viewitems()` | Returns a dict_items on the dictionary's items
    `PyObject` | `viewkeys()` | Returns a dict_keys on the dictionary's keys
    `PyObject` | `viewvalues()` | Returns a dict_values on the dictionary's values

    - ### Methods inherited from class org.python.core.PyObject

      `__abs__, __add__, __and__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __call__, __coerce__, __coerce_ex__, __complex__, __delattr__, __delattr__, __delete__, __delitem__, __delslice__, __delslice__, __dir__, __div__, __divmod__, __ensure_finalizer__, __findattr__, __findattr__, __findattr_ex__, __finditem__, __float__, __floordiv__, __format__, __ge__, __get__, __getattr__, __getattr__, __getitem__, __getitem__, __getnewargs__, __getslice__, __getslice__, __gt__, __hash__, __hex__, __iadd__, __iand__, __idiv__, __idivmod__, __ifloordiv__, __ilshift__, __imod__, __imul__, __index__, __int__, __invert__, __ior__, __ipow__, __irshift__, __isub__, __iternext__, __itruediv__, __ixor__, __le__, __long__, __lshift__, __lt__, __mod__, __mul__, __neg__, __not__, __oct__, __or__, __pos__, __pow__, __pow__, __radd__, __rand__, __rdiv__, __rdivmod__, __reduce__, __reduce_ex__, __reduce_ex__, __repr__, __rfloordiv__, __rlshift__, __rmod__, __rmul__, __ror__, __rpow__, __rrshift__, __rshift__, __rsub__, __rtruediv__, __rxor__, __set__, __setattr__, __setattr__, __setitem__, __setitem__, __setslice__, __setslice__, __str__, __sub__, __tojava__, __truediv__, __trunc__, __unicode__, __xor__, _add, _and, _callextra, _cmp, _div, _divmod, _doget, _doget, _doset, _eq, _floordiv, _ge, _gt, _iadd, _iand, _idiv, _idivmod, _ifloordiv, _ilshift, _imod, _imul, _in, _ior, _ipow, _irshift, _is, _isnot, _isub, _itruediv, _ixor, _jcall, _jcallexc, _jthrow, _le, _lshift, _lt, _mod, _mul, _ne, _notin, _or, _pow, _rshift, _sub, _truediv, _xor, asDouble, asIndex, asIndex, asInt, asInt, asIterable, asLong, asLong, asName, asName, asString, asString, asStringOrNull, asStringOrNull, bit_length, conjugate, delDict, delType, dispatch__init__, fastGetClass, fastGetDict, getDict, getType, implementsDescrDelete, implementsDescrGet, implementsDescrSet, invoke, invoke, invoke, invoke, invoke, invoke, isCallable, isDataDescr, isIndex, isInteger, isNumberType, noAttributeError, object___subclasshook__, readonlyAttributeError, setDict, setType`

    - ### Methods inherited from class java.lang.Object

      `getClass, notify, notifyAll, wait, wait, wait`

    - ### Methods inherited from interface java.util.concurrent.ConcurrentMap

      `compute, computeIfAbsent, computeIfPresent, forEach, getOrDefault, merge, replaceAll`

- - ### Field Detail

    - #### TYPE

          public static final PyType TYPE

  - ### Constructor Detail

    - #### PyDictionary

          public PyDictionary()

      Create an empty dictionary.

    - #### PyDictionary

          public PyDictionary​(PyType type,
                              int capacity)

      Create a dictionary of type with the specified initial capacity.

    - #### PyDictionary

          public PyDictionary​(PyType type)

      For derived types

    - #### PyDictionary

          public PyDictionary​(java.util.Map<PyObject,​PyObject> map)

      Create a new dictionary which is based on given map.

    - #### PyDictionary

          public PyDictionary​(java.util.concurrent.ConcurrentMap<PyObject,​PyObject> backingMap,
                              boolean useBackingMap)

    - #### PyDictionary

          public PyDictionary​(PyType type,
                              java.util.concurrent.ConcurrentMap<PyObject,​PyObject> backingMap,
                              boolean useBackingMap)

    - #### PyDictionary

          public PyDictionary​(PyType type,
                              java.util.Map<PyObject,​PyObject> map)

      Create a new dictionary which is populated with entries the given map.

    - #### PyDictionary

          public PyDictionary​(PyObject[] elements)

      Create a new dictionary with the element as content.
      Parameters:
        `elements` - The initial elements that is inserted in the dictionary. Even numbered elements are keys, odd numbered elements are values.

  - ### Method Detail

    - #### getMap

          public java.util.concurrent.ConcurrentMap<PyObject,​PyObject> getMap()

      Specified by:
        `getMap` in class `AbstractDict`

    - #### fromkeys

          public static PyObject fromkeys​(PyObject keys)

    - #### fromkeys

          public static PyObject fromkeys​(PyObject keys,
                                          PyObject value)

    - #### __len__

          public int __len__()

      Description copied from class: `PyObject`
      Equivalent to the standard Python __len__ method. Part of the mapping discipline.
      Overrides:
        `__len__` in class `PyObject`
      Returns:
        the length of the object

    - #### __nonzero__

          public boolean __nonzero__()

      Description copied from class: `PyObject`
      Equivalent to the standard Python __nonzero__ method. Returns whether of not a given `PyObject` is considered true.
      Overrides:
        `__nonzero__` in class `PyObject`

    - #### __finditem__

          public PyObject __finditem__​(int index)

      Description copied from class: `PyObject`
      A variant of the __finditem__ method which accepts a primitive `int` as the key. By default, this method will call `__finditem__(PyObject key)` with the appropriate args. The only reason to override this method is for performance.
      Overrides:
        `__finditem__` in class `PyObject`
      Parameters:
        `index` - the key to lookup in this sequence.
      Returns:
        the value corresponding to key or null if key is not found.
      See Also:
        `PyObject.__finditem__(PyObject)`

    - #### __finditem__

          public PyObject __finditem__​(PyObject key)

      Description copied from class: `PyObject`
      Very similar to the standard Python __getitem__ method. Instead of throwing a KeyError if the item isn't found, this just returns null. Classes that wish to implement __getitem__ should override this method instead (with the appropriate semantics.
      Overrides:
        `__finditem__` in class `PyObject`
      Parameters:
        `key` - the key to lookup in this container
      Returns:
        the value corresponding to key or null if key is not found

    - #### __setitem__

          public void __setitem__​(PyObject key,
                                  PyObject value)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __setitem__ method.
      Overrides:
        `__setitem__` in class `PyObject`
      Parameters:
        `key` - the key whose value will be set
        `value` - the value to set this key to

    - #### __delitem__

          public void __delitem__​(PyObject key)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __delitem__ method.
      Overrides:
        `__delitem__` in class `PyObject`
      Parameters:
        `key` - the key to be removed from the container

    - #### __iter__

          public PyObject __iter__()

      Description copied from class: `PyObject`
      Return an iterator that is used to iterate the element of this sequence. From version 2.2, this method is the primary protocol for looping over sequences.

      If a PyObject subclass should support iteration based in the __finditem__() method, it must supply an implementation of __iter__() like this:

           public PyObject __iter__() {
               return new PySequenceIter(this);
           }

      When iterating over a python sequence from java code, it should be done with code like this:

           for (PyObject item : seq.asIterable()) {
               // Do something with item
           }

      Overrides:
        `__iter__` in class `PyObject`

    - #### toString

          public java.lang.String toString()

      Overrides:
        `toString` in class `PyObject`

    - #### __eq__

          public PyObject __eq__​(PyObject otherObj)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __eq__ method.
      Overrides:
        `__eq__` in class `PyObject`
      Parameters:
        `otherObj` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __ne__

          public PyObject __ne__​(PyObject otherObj)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __ne__ method.
      Overrides:
        `__ne__` in class `PyObject`
      Parameters:
        `otherObj` - the object to compare this with.
      Returns:
        the result of the comparison.

    - #### __cmp__

          public int __cmp__​(PyObject otherObj)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __cmp__ method.
      Overrides:
        `__cmp__` in class `PyObject`
      Parameters:
        `otherObj` - the object to compare this with.
      Returns:
        -1 if `this<o`; 0 if `this==o`; +1 if `this>o`; -2 if no comparison is implemented

    - #### has_key

          public boolean has_key​(PyObject key)

      Return true if the key exist in the dictionary.
      Specified by:
        `has_key` in class `AbstractDict`

    - #### __contains__

          public boolean __contains__​(PyObject o)

      Description copied from class: `PyObject`
      Equivalent to the standard Python __contains__ method.
      Overrides:
        `__contains__` in class `PyObject`
      Parameters:
        `o` - the element to search for in this container.
      Returns:
        the result of the search.

    - #### get

          public PyObject get​(PyObject key,
                              PyObject defaultObj)

      Return this[key] if the key exists in the mapping, defaultObj is returned otherwise.
      Specified by:
        `get` in class `AbstractDict`
      Parameters:
        `key` - the key to lookup in the dictionary.
        `defaultObj` - the value to return if the key does not exists in the mapping.

    - #### get

          public PyObject get​(PyObject key)

      Return this[key] if the key exists in the mapping, None is returned otherwise.
      Specified by:
        `get` in class `AbstractDict`
      Parameters:
        `key` - the key to lookup in the dictionary.

    - #### copy

          public PyDictionary copy()

      Return a shallow copy of the dictionary.
      Specified by:
        `copy` in class `AbstractDict`

    - #### clear

          public void clear()

      Remove all items from the dictionary.
      Specified by:
        `clear` in interface `java.util.Map`
      Specified by:
        `clear` in class `AbstractDict`

    - #### update

          public void update​(PyObject other)

      Insert all the key:value pairs from `d` into this dictionary.
      Specified by:
        `update` in class `AbstractDict`

    - #### updateCommon

          public void updateCommon​(PyObject[] args,
                                   java.lang.String[] keywords,
                                   java.lang.String methName)

    - #### merge

          public void merge​(PyObject other,
                            boolean override)

      Merge another PyObject that supports keys() with this dict.
      Specified by:
        `merge` in class `AbstractDict`
      Parameters:
        `other` - a PyObject with a keys() method
        `override` - if true, the value from other is used on key-collision

    - #### mergeFromKeys

          public void mergeFromKeys​(PyObject other,
                                    PyObject keys,
                                    boolean override)

      Merge another PyObject via its keys() method
      Specified by:
        `mergeFromKeys` in class `AbstractDict`
      Parameters:
        `other` - a PyObject with a keys() method
        `keys` - the result of other's keys() method
        `override` - if true, the value from other is used on key-collision

    - #### mergeFromSeq

          public void mergeFromSeq​(PyObject other,
                                   boolean override)

      Merge any iterable object producing iterable objects of length 2 into this dict.
      Specified by:
        `mergeFromSeq` in class `AbstractDict`
      Parameters:
        `other` - another PyObject
        `override` - if true, the value from other is used on key-collision

    - #### setdefault

          public PyObject setdefault​(PyObject key)

      Return this[key] if the key exist, otherwise insert key with a None value and return None.
      Specified by:
        `setdefault` in class `AbstractDict`
      Parameters:
        `key` - the key to lookup in the dictionary.

    - #### setdefault

          public PyObject setdefault​(PyObject key,
                                     PyObject failobj)

      Return this[key] if the key exist, otherwise insert key with the value of failobj and return failobj
      Specified by:
        `setdefault` in class `AbstractDict`
      Parameters:
        `key` - the key to lookup in the dictionary.
        `failobj` - the default value to insert in the dictionary if key does not already exist.

    - #### pop

          public PyObject pop​(PyObject key)

      Return a value based on key from the dictionary.
      Specified by:
        `pop` in class `AbstractDict`

    - #### pop

          public PyObject pop​(PyObject key,
                              PyObject defaultValue)

      Return a value based on key from the dictionary or default if that key is not found.
      Specified by:
        `pop` in class `AbstractDict`

    - #### popitem

          public PyObject popitem()

      Return a random (key, value) tuple pair and remove the pair from the dictionary.
      Specified by:
        `popitem` in class `AbstractDict`

    - #### items

          public PyList items()

      Return a copy of the dictionary's list of (key, value) tuple pairs.
      Specified by:
        `items` in class `AbstractDict`

    - #### keys

          public PyList keys()

      Return a copy of the dictionary's list of keys.
      Specified by:
        `keys` in class `AbstractDict`

    - #### iteritems

          public PyObject iteritems()

      Returns an iterator over (key, value) pairs.
      Specified by:
        `iteritems` in class `AbstractDict`

    - #### iterkeys

          public PyObject iterkeys()

      Returns an iterator over the dictionary's keys.
      Specified by:
        `iterkeys` in class `AbstractDict`

    - #### itervalues

          public PyObject itervalues()

      Returns an iterator over the dictionary's values.
      Specified by:
        `itervalues` in class `AbstractDict`

    - #### hashCode

          public int hashCode()

      Specified by:
        `hashCode` in interface `java.util.Map`
      Overrides:
        `hashCode` in class `PyObject`

    - #### equals

          public boolean equals​(java.lang.Object obj)

      Description copied from class: `PyObject`
      Should almost never be overridden. If overridden, it is the subclasses responsibility to ensure that `a.equals(b) == true` iff `cmp(a,b) == 0`
      Specified by:
        `equals` in interface `java.util.Map`
      Overrides:
        `equals` in class `PyObject`

    - #### isMappingType

          public boolean isMappingType()

      Overrides:
        `isMappingType` in class `PyObject`

    - #### isSequenceType

          public boolean isSequenceType()

      Overrides:
        `isSequenceType` in class `PyObject`

    - #### viewkeys

          public PyObject viewkeys()

      Returns a dict_keys on the dictionary's keys
      Overrides:
        `viewkeys` in class `AbstractDict`

    - #### viewitems

          public PyObject viewitems()

      Returns a dict_items on the dictionary's items
      Overrides:
        `viewitems` in class `AbstractDict`

    - #### viewvalues

          public PyObject viewvalues()

      Returns a dict_values on the dictionary's values
      Overrides:
        `viewvalues` in class `AbstractDict`

    - #### pyKeySet

          public java.util.Set<PyObject> pyKeySet()

      Specified by:
        `pyKeySet` in class `AbstractDict`

    - #### entrySet

          public java.util.Set entrySet()

      Specified by:
        `entrySet` in interface `java.util.Map`
      Specified by:
        `entrySet` in class `AbstractDict`
      See Also:
        `Map.entrySet()`

    - #### keySet

          public java.util.Set keySet()

      Specified by:
        `keySet` in interface `java.util.Map`
      See Also:
        `Map.keySet()`

    - #### values

          public java.util.Collection values()

      Specified by:
        `values` in interface `java.util.Map`
      Specified by:
        `values` in class `AbstractDict`
      See Also:
        `Map.values()`

    - #### putAll

          public void putAll​(java.util.Map map)

      Specified by:
        `putAll` in interface `java.util.Map`
      See Also:
        `Map.putAll(Map map)`

    - #### remove

          public java.lang.Object remove​(java.lang.Object key)

      Specified by:
        `remove` in interface `java.util.Map`
      See Also:
        `Map.remove(Object key)`

    - #### put

          public java.lang.Object put​(java.lang.Object key,
                                      java.lang.Object value)

      Specified by:
        `put` in interface `java.util.Map`
      See Also:
        `Map.put(Object key, Object value)`

    - #### get

          public java.lang.Object get​(java.lang.Object key)

      Specified by:
        `get` in interface `java.util.Map`
      See Also:
        `Map.get(Object key)`

    - #### containsValue

          public boolean containsValue​(java.lang.Object value)

      Specified by:
        `containsValue` in interface `java.util.Map`
      See Also:
        `Map.containsValue(Object key)`

    - #### containsKey

          public boolean containsKey​(java.lang.Object key)

      Specified by:
        `containsKey` in interface `java.util.Map`
      See Also:
        `Map.containsValue(Object key)`

    - #### isEmpty

          public boolean isEmpty()

      Specified by:
        `isEmpty` in interface `java.util.Map`
      See Also:
        `Map.isEmpty()`

    - #### size

          public int size()

      Specified by:
        `size` in interface `java.util.Map`
      See Also:
        `Map.size()`

    - #### putIfAbsent

          public java.lang.Object putIfAbsent​(java.lang.Object key,
                                              java.lang.Object value)

      Specified by:
        `putIfAbsent` in interface `java.util.concurrent.ConcurrentMap`
      Specified by:
        `putIfAbsent` in interface `java.util.Map`

    - #### remove

          public boolean remove​(java.lang.Object key,
                                java.lang.Object value)

      Specified by:
        `remove` in interface `java.util.concurrent.ConcurrentMap`
      Specified by:
        `remove` in interface `java.util.Map`

    - #### replace

          public boolean replace​(java.lang.Object key,
                                 java.lang.Object oldValue,
                                 java.lang.Object newValue)

      Specified by:
        `replace` in interface `java.util.concurrent.ConcurrentMap`
      Specified by:
        `replace` in interface `java.util.Map`

    - #### replace

          public java.lang.Object replace​(java.lang.Object key,
                                          java.lang.Object value)

      Specified by:
        `replace` in interface `java.util.concurrent.ConcurrentMap`
      Specified by:
        `replace` in interface `java.util.Map`

    - #### traverse

          public int traverse​(Visitproc visit,
                              java.lang.Object arg)

      Description copied from interface: `Traverseproc`
      Traverses all directly contained `PyObject`s. Like in CPython, `arg` must be passed unmodified to `visit` as its second parameter. If `Visitproc.visit(PyObject, Object)` returns nonzero, this return value must be returned immediately by traverse. `Visitproc.visit(PyObject, Object)` must not be called with a `null` PyObject-argument.
      Specified by:
        `traverse` in interface `Traverseproc`

    - #### refersDirectlyTo

          public boolean refersDirectlyTo​(PyObject ob)

      Description copied from interface: `Traverseproc`
      Optional operation. Should only be implemented if it is more efficient than calling `Traverseproc.traverse(Visitproc, Object)` with a visitproc that just watches out for `ob`. Must return `false` if `ob` is `null`.
      Specified by:
        `refersDirectlyTo` in interface `Traverseproc`