anchor.diff:  -module(mongo).
   -export([
     connect/1,
  +  connect/2,
     connect/3,
     connect/5,
     connect/6,  %TODO disconnect?
  
positive.code:   case bson:lookup('_id', Doc) of
      {_Value} -> Doc;
      {} -> bson:update('_id', mongo_id_server:object_id(), Doc)
    end.
negative.code: -spec connect(database()) -> {ok, pid()}.
  connect(Database) ->
    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(
  