code: def _get_sender(*sender_params, **kwargs):
      
      notify_func = kwargs['notify_func']
      with _sender_instances_lock:
          existing_sender = _sender_instances.get(sender_params, None)
          if existing_sender:
              sender = existing_sender
              sender._notify = notify_func
          else:
              sender = _Sender(*sender_params, notify=notify_func)
          _sender_instances[sender_params] = sender
          return sender
docs: Utility function acting as a Sender factory - ensures senders don't get
      created twice of more for the same target server