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

        :param family_ids: list of families
        :type family_ids: ``osid.id.IdList``
        :raise: ``NullArgument`` -- ``family_ids`` is ``null``

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