@abc.abstractmethod<EOL><INDENT>def get_agent_agency_assignment_session(self):<DEDENT>
return<EOL>
Gets the session for assigning agent to agency mappings.

        :return: a ``AgentAgencyAsignmentSession``
        :rtype: ``osid.authentication.AgentAgencyAssignmentSession``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``Unimplemented`` -- ``supports_agent_agency_assignment()`` is ``false``

        *compliance: optional -- This method must be implemented if
        ``supports_agent_agency_assignment()`` is ``true``.*