code: def _append_object_entry(obj, list_name, entry):
      # type: (Any, str, Any) -> None
      
      # Get the list
      obj_list = getattr(obj, list_name, None)
      if obj_list is None:
          # We'll have to create it
          obj_list = []
          setattr(obj, list_name, obj_list)
  
      assert isinstance(obj_list, list)
  
      # Set up the property, if needed
      if entry not in obj_list:
          obj_list.append(entry)
docs: Appends the given entry in the given object list.
      Creates the list field if needed.
  
      :param obj: The object that contains the list
      :param list_name: The name of the list member in *obj*
      :param entry: The entry to be added to the list
      :raise ValueError: Invalid attribute content