@abc.abstractmethod<EOL><INDENT>def get_agents_by_parent_genus_type(self, agent_genus_type):<DEDENT>
return<EOL>
Gets an ``AgentList`` corresponding to the given agent genus ``Type`` and include any additional agents with genus types derived from the specified ``Type``.

        In plenary mode, the returned list contains all known agents or
        an error results. Otherwise, the returned list may contain only
        those agents that are accessible through this session.

        :param agent_genus_type: an agent genus type
        :type agent_genus_type: ``osid.type.Type``
        :return: the returned ``Agent`` list
        :rtype: ``osid.authentication.AgentList``
        :raise: ``NullArgument`` -- ``agent_genus_type`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

        *compliance: mandatory -- This method must be implemented.*