# Source code for pint.facets.group.definitions

    """
        pint.facets.group.definitions
        ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

        :copyright: 2022 by Pint Authors, see AUTHORS for more details.
        :license: BSD, see LICENSE for more details.
    """

    from __future__ import annotations

    from collections.abc import Iterable
    from dataclasses import dataclass

    from ... import errors
    from ...compat import Self
    from .. import plain

    @dataclass(frozen=True)
    class GroupDefinition(errors.WithDefErr):
        """Definition of a group."""

        #: name of the group
        name: str
        #: unit groups that will be included within the group
        using_group_names: tuple[str, ...]
        #: definitions for the units existing within the group
        definitions: tuple[plain.UnitDefinition, ...]

        @classmethod
        def from_lines(
            cls: type[Self], lines: Iterable[str], non_int_type: type
        ) -> Self | None:
            # TODO: this is to keep it backwards compatible
            from ...delegates import ParserConfig, txt_defparser

            cfg = ParserConfig(non_int_type)
            parser = txt_defparser.DefParser(cfg, None)
            pp = parser.parse_string("\n".join(lines) + "\n@end")
            for definition in parser.iter_parsed_project(pp):
                if isinstance(definition, cls):
                    return definition

        @property
        def unit_names(self) -> tuple[str, ...]:
            return tuple(el.name for el in self.definitions)

        def __post_init__(self) -> None:
            if not errors.is_valid_group_name(self.name):
                raise self.def_err(errors.MSG_INVALID_GROUP_NAME)

            for k in self.using_group_names:
                if not errors.is_valid_group_name(k):
                    raise self.def_err(
                        f"refers to '{k}' that " + errors.MSG_INVALID_GROUP_NAME
                    )