@utilities.arguments_not_none<EOL><INDENT>def search_among_families(self, family_ids):<DEDENT>
self._id_list = family_ids<EOL>
Execute this search among the given list of families.

        arg:    family_ids (osid.id.IdList): list of families
        raise:  NullArgument - ``family_ids`` is ``null``
        *compliance: mandatory -- This method must be implemented.*