@abc.abstractmethod<EOL><INDENT>def search_among_agencies(self, agency_ids):<DEDENT>
pass<EOL>
Execute this search among the given list of agencies.

        :param agency_ids: list of agencies
        :type agency_ids: ``osid.id.IdList``
        :raise: ``NullArgument`` -- ``agency_ids`` is ``null``

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