mongodb-client-encryption expects this to be present: https://github.com/mongodb/libmongocrypt/blob/6862668722a05a8d80a8fab9aef20478810d28b7/bindings/node/lib/clientEncryption.js#L104

(This could also be addressed in libmongocrypt, but in the interest of easier upgrade paths, it seems like adding this back to the Topology class would be a good solution for the near future.)