docs: def get_children_metadata(self):
          """Gets the metadata for children.
  
          return: (osid.Metadata) - metadata for the children
          *compliance: mandatory -- This method must be implemented.*
  
          """
          metadata = dict(self._mdata['children'])
          metadata.update({'existing_children_values': self._my_map['childIds']})
          return Metadata(**metadata)