anchor.diff:  %% with Reason. The return value is ignored.
   %% @end
   %%--------------------------------------------------------------------
  --spec terminate(Reason, State :: term()) -> Any :: term() when
  +-spec terminate(Reason, State :: state()) -> Any :: term() when
       Reason :: normal
       | shutdown
       | {shutdown, term()}
  
positive.code: %% Checks if singleton module can be started.
  %% @end
  %%--------------------------------------------------------------------
  -spec register_singleton_module(Module :: atom(), Node :: node(), State :: #state{}) ->
      {ok | already_started, #state{}}.
  register_singleton_module(Module, Node, #state{singleton_modules = Singletons} = State) ->
      UsedNode = proplists:get_value(Module, Singletons),
      case UsedNode of
  
negative.code: %% @end
  %%--------------------------------------------------------------------
  -spec handle_call(Request :: term(), From :: {pid(), Tag :: term()},
      State :: state()) -> Result when
      Result :: {reply, Reply, NewState}
      | {reply, Reply, NewState, Timeout}
      | {reply, Reply, NewState, hibernate}
  