'Starts the callback server.
:param callback_server_parameters: parameters to use to start the
server. If not provided, it will use the gateway callback server
parameters.
:rtype: Returns True if the server was started by this call or False if
it was already started (you cannot have more than one started
callback server).'

def start_callback_server(self, callback_server_parameters=None):

    if self._callback_server:
        return False
    if (not callback_server_parameters):
        callback_server_parameters = self.callback_server_parameters
    self._callback_server = CallbackServer(self.gateway_property.pool, self._gateway_client, callback_server_parameters=callback_server_parameters)
    try:
        self._callback_server.start()
    except Py4JNetworkError:
        self.shutdown()
        self._callback_server = None
        raise
    return True
