anchor.diff:  -behaviour(gen_server).
   
   %% API
  --export([start_link/1,
  +-export([start_link/0,
            write/2,
  -         read/1]).
  +         read/1,
  +         update/1]).
   
   %% gen_server callbacks
   -export([init/1,
  
positive.code:          terminate/2,
           code_change/3]).
  
  -record(state, {store, nodes=[]}).
  
  -include("partisan.hrl").
  
  
negative.code:     {noreply, State};
  
  %% @private
  handle_info({collaborate, {FromPid, FromRequestId}=From, SourceNode, Key, Value}, #state{membership=[_Primary, _Collaborator | Backups], store=Store0}=State) ->
      %% Write value locally.
      Store = write(Key, Value, Store0),
      lager:info("~p: node ~p storing updated value key ~p value ~p", [?MODULE, node(), Key, Value]),
  