'The custom payload returned from the server, if any. This will only be
set by Cassandra servers implementing a custom QueryHandler, and only
for protocol_version 4+.
Ensure the future is complete before trying to access this property
(call :meth:`.result()`, or after callback is invoked).
Otherwise it may throw if the response has not been received.
:return: :ref:`custom_payload`.'

@property
def custom_payload(self):

    if (not self._event.is_set()):
        raise DriverException('custom_payload    cannot    be    retrieved    before    ResponseFuture    is    finalized')
    return self._custom_payload
