Motor's Sphinx extensions complain about a few of the current docstrings:
$ python3.7 -m tox -e py3-sphinx-docs ... PyMongo docstrings with code blocks that need update: motor.motor_asyncio.AsyncIOMotorClient.fsync motor.motor_asyncio.AsyncIOMotorDatabase.current_op motor.motor_asyncio.AsyncIOMotorDatabase.list_collection_names motor.motor_tornado.MotorClient.fsync motor.motor_tornado.MotorDatabase.current_op motor.motor_tornado.MotorDatabase.list_collection_names