def get_families_by_query(self, family_query=None):
pass<EOL>
Gets a list of ``Family`` objects matching the given family query.

        arg:    family_query (osid.relationship.FamilyQuery): the family
                query
        return: (osid.relationship.FamilyList) - the returned
                ``FamilyList``
        raise:  NullArgument - ``family_query`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  PermissionDenied - authorization failure
        raise:  Unsupported - ``family_query`` is not of this service
        *compliance: mandatory -- This method must be implemented.*