docs: def _load_child_state_models(self, load_meta_data):
          """Adds models for each child state of the state
  
          :param bool load_meta_data: Whether to load the meta data of the child state
          """
          self.states = {}
          # Create model for each child class
          child_states = self.state.states
          for child_state in child_states.values():
              # Create hierarchy
              model_class = get_state_model_class_for_state(child_state)
              if model_class is not None:
                  self._add_model(self.states, child_state, model_class, child_state.state_id, load_meta_data)
              else:
                  logger.error("Unknown state type '{type:s}'. Cannot create model.".format(type=type(child_state)))