code: def alpha_senders(self):
          
          if self._alpha_senders is None:
              self._alpha_senders = AlphaSenderList(self._version, service_sid=self._solution['sid'], )
          return self._alpha_senders
docs: Access the alpha_senders
  
          :returns: twilio.rest.messaging.v1.service.alpha_sender.AlphaSenderList
          :rtype: twilio.rest.messaging.v1.service.alpha_sender.AlphaSenderList