code: def get_children(self, id_):
          
          id_list = []
          for r in self._rls.get_relationships_by_genus_type_for_source(id_, self._relationship_type):
              id_list.append(r.get_destination_id())
          return IdList(id_list)
docs: Gets the children of the given ``Id``.
  
          arg:    id (osid.id.Id): the ``Id`` to query
          return: (osid.id.IdList) - the children of the ``id``
          raise:  NotFound - ``id`` is not found
          raise:  NullArgument - ``id`` is ``null``
          raise:  OperationFailed - unable to complete request
          raise:  PermissionDenied - authorization failure
          *compliance: mandatory -- This method must be implemented.*