anchor.diff:  insert(Connection, Coll, Doc) when is_tuple(Doc) ->
     hd(insert(Connection, Coll, [Doc]));
   insert(Connection, Coll, Docs) ->
  -  Docs1 = [assign_id(Doc) || Doc <- Docs],
  +  Converted = prepare_doc(Docs),
  +  Docs1 = [assign_id(Doc) || Doc <- Converted],
     mc_connection_man:request_async(Connection, #insert{collection = Coll, documents = Docs1}),
     Docs1.
   
  
positive.code:     {_Value} -> Doc;
      {} -> bson:update('_id', mongo_id_server:object_id(), Doc)
    end.
  
negative.code:   mc_worker:start_link([{database, Database}]).
  -spec connect(database(), proplists:proplist()) -> {ok, pid()}.
  connect(Database, Opts) ->
    mc_worker:start_link(lists:append(Opts, [{database, Database}])).
  -spec connect(database(), bson:utf8(), bson:utf8()) -> {ok, pid()}.
  connect(Database, User, Pass) ->
    mc_worker:start_link(
  