code: def tube(self, name):
          
          if name in self._tubes:
              return self._tubes[name]
  
          assert name, 'Tube name must be specified'
          t = self._tube_cls(self, name)
          self._tubes[name] = t
          return t
docs: Returns tube by its name
  
              :param name: Tube name
              :returns: ``self.tube_cls`` instance
                  (by default :class:`asynctnt_queue.Tube`)