'Dequeues a member from the queue and have the member\'s call
begin executing the TwiML document at the url.
:param call_sid: Call sid specifying the member, if not given,
the member at the front of the queue will be used
:param url: url of the TwiML document to be executed.'

def dequeue(self, url, call_sid='Front', **kwargs):

    kwargs['url'] = url
    return self.update_instance(call_sid, kwargs)
