Log in to the server and store these credentials in `authset`.

        Can raise ConnectionFailure or OperationFailure.

        :Parameters:
          - `credentials`: A MongoCredential.

def authenticate(self, credentials):
        """Log in to the server and store these credentials in `authset`.

        Can raise ConnectionFailure or OperationFailure.

        :Parameters:
          - `credentials`: A MongoCredential.
        """
        auth.authenticate(credentials, self)
        self.authset.add(credentials)