code: function(callback)
      {
          // Connect to the given URI with the given options
          self.mongo.MongoClient.connect(self.config.uri, defaultOpts, function(err, db) {
  
              if (err) {
                  return callback && callback(err);
              }
  
              // Rewrite connection
              self.connection = db;
  
              callback && callback(null, db);
          });
      }
docs: Setup the plain MongoDB connection