@abc.abstractmethod<EOL><INDENT>def get_agents_by_agencies(self, agency_ids):<DEDENT>
return<EOL>
Gets the list of ``Agents`` corresponding to a list of ``Agency`` objects.

        :param agency_ids: list of agency ``Ids``
        :type agency_ids: ``osid.id.IdList``
        :return: list of agents
        :rtype: ``osid.authentication.AgentList``
        :raise: ``NullArgument`` -- ``agency_ids`` is ``null``
        :raise: ``OperationFailed`` -- unable to complete request
        :raise: ``PermissionDenied`` -- authorization failure

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