docs: def combine_lists_reducer(
          key: str,
          merged_list: list,
          component: COMPONENT
  ) -> list:
      """
      Reducer function to combine the lists for the specified key into a
      single, flat list
  
      :param key:
          The key on the COMPONENT instances to operate upon
      :param merged_list:
          The accumulated list of values populated by previous calls to this
          reducer function
      :param component:
          The COMPONENT instance from which to append values to the
          merged_list
      :return:
          The updated merged_list with the values for the COMPONENT added
          onto it
      """
  
      merged_list.extend(getattr(component, key))
      return merged_list