@abc.abstractmethod<EOL><INDENT>def search_among_hierarchies(self, hierarchy_ids):<DEDENT>
pass<EOL>
Execute this search using a given list of hierarchies.

        :param hierarchy_ids: list of hierarchies
        :type hierarchy_ids: ``osid.id.IdList``
        :raise: ``NullArgument`` -- ``hierarchy_ids`` is ``null``

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