# Source code for aiohttp_security.abc

    import abc

    # see http://plope.com/pyramid_auth_design_api_postmortem

    class AbstractIdentityPolicy(metaclass=abc.ABCMeta):

        @abc.abstractmethod
        async def identify(self, request):
            """Return the claimed identity of the user associated request or
            ``None`` if no identity can be found associated with the request."""
            pass

        @abc.abstractmethod
        async def remember(self, request, response, identity, **kwargs):
            """Remember identity.

            Modify response object by filling it's headers with remembered user.

            An individual identity policy and its consumers can decide on
            the composition and meaning of **kwargs.
            """
            pass

        @abc.abstractmethod
        async def forget(self, request, response):
            """ Modify response which can be used to 'forget' the
            current identity on subsequent requests."""
            pass

    class AbstractAuthorizationPolicy(metaclass=abc.ABCMeta):

        @abc.abstractmethod
        async def permits(self, identity, permission, context=None):
            """Check user permissions.

            Return True if the identity is allowed the permission in the
            current context, else return False.
            """
            pass

        @abc.abstractmethod
        async def authorized_userid(self, identity):
            """Retrieve authorized user id.

            Return the user_id of the user identified by the identity
            or 'None' if no user exists related to the identity.
            """
            pass