The latest version shows the following warning:

DeprecationWarning: current Server Discovery and Monitoring engine is deprecated, and will be removed in a future version. To use the new Server Discover and Monitoring engine, pass option { useUnifiedTopology: true } to MongoClient.connect.

Reading this, one might assume that this options has to be passed to the connect method:

new MongoClient(connectionUri).connect({ useUnifiedTopology: true })

That doesn't work, however, because options can only be passed to the constructor:

new MongoClient(connectionUri, { useUnifiedTopology: true }).connect()

The deprecation warning should be changed to be less confusing.