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