@abc.abstractmethod<EOL><INDENT>def get_families_by_query(self, family_query):<DEDENT>
return<EOL>
Gets a list of ``Family`` objects matching the given family query.

        :param family_query: the family query
        :type family_query: ``osid.relationship.FamilyQuery``
        :return: the returned ``FamilyList``
        :rtype: ``osid.relationship.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.*