anchor.diff:      {ok, #state{nodes=Nodes, store=Store}}.
   
   %% @private
  -handle_call({write, Key, Value}, From, #state{nodes=[Node|Rest], store=Store0}=State) ->
  +handle_call({write, Key, Value}, From, #state{nodes=[Node, Collaborator|_Rest], store=Store0}=State) ->
       case node() of 
           Node ->
               lager:info("~p: node ~p received write for key ~p with value ~p", [?MODULE, node(), Key, Value]),
  
positive.code:     {noreply, State}.
  
  %% @private
  handle_info({ack, From, Key, Value}, State) ->
      lager:info("~p: node ~p ack received for key ~p value ~p", [?MODULE, node(), Key, Value]),
  
      %% On ack, reply to caller.
      gen_server:reply(From, ok),
  
      {noreply, State};
  handle_info({update, From, FromNode, Key, Value}, #state{store=Store0}=State) ->
      %% Write value locally.
      Store = dict:store(Key, Value, Store0),
      lager:info("~p: node ~p storing updated value key ~p value ~p", [?MODULE, node(), Key, Value]),
  
      %% Send write acknowledgement.
      Manager = partisan_config:get(partisan_peer_service_manager),
      ok = Manager:forward_message(FromNode, undefined, ?MODULE, {ack, From, Key, Value}, []),
      lager:info("~p: node ~p acknowledging value for key ~p value ~p", [?MODULE, node(), Key, Value]),
  
      {noreply, State#state{store=Store}};
  
negative.code:             %% Write value locally.
              Store = dict:store(Key, Value, Store0),
  
              %% Forward to collaboration message.
              FromNode = partisan_peer_service_manager:myself(),
              Manager = partisan_config:get(partisan_peer_service_manager),
              ok = Manager:forward_message(Collaborator, undefined, ?MODULE, {collaborate, From, FromNode, Key, Value}, []),
              lager:info("~p: node ~p sent replication request for key ~p with value ~p", [?MODULE, node(), Key, Value]),
  
              {noreply, State#state{store=Store}};
  