docs: def register_members(self):
          """Collect the names of the class member and convert them to object
          members.
  
          Unlike Terms, the Group class members are converted into object
          members, so the configuration data
  
          """
  
          self._members = {
              name: attr for name, attr in iteritems(type(self).__dict__) if isinstance(attr, Group)}
  
          for name, m in iteritems(self._members):
              m.init_descriptor(name, self)