code: def is_child(self, id_, child_id):
          
          return bool(self._rls.get_relationships_by_genus_type_for_peers(
              id_,
              child_id,
              self._relationship_type).available())
docs: Tests if a node is a direct child of another.
  
          arg:    id (osid.id.Id): the ``Id`` to query
          arg:    child_id (osid.id.Id): the ``Id`` of a child
          return: (boolean) - ``true`` if this ``child_id`` is a child of
                  the ``Id,``  ``false`` otherwise
          raise:  NotFound - ``id`` is not found
          raise:  NullArgument - ``id`` or ``child_id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*
          *implementation notes*: If ``child_id`` not found return
          ``false``.