code: function logout(mongoClient, dbName, callback) {
    mongoClient.topology.logout(dbName, err => {
      if (err) return callback(err);
      callback(null, true);
    });
  }
docs: Logout user from server, fire off on all connections and remove all auth info.
  
  @method
  @param {MongoClient} mongoClient The MongoClient instance on which to logout.
  @param {object} [options] Optional settings. See MongoClient.prototype.logout for a list of options.
  @param {Db~resultCallback} [callback] The command result callback