code: def poll(self):
          
          if self.complete:
              raise ValueError("The operation has completed.")
  
          operation_pb = self._get_operation()
          self._update_state(operation_pb)
  
          return self.complete
docs: Check if the operation has finished.
  
          :rtype: bool
          :returns: A boolean indicating if the current operation has completed.
          :raises ValueError: if the operation
                   has already completed.