code: def _blocking_poll(self, timeout=None):
          
          if self._result_set:
              return
  
          retry_ = self._retry.with_deadline(timeout)
  
          try:
              retry_(self._done_or_raise)()
          except exceptions.RetryError:
              raise concurrent.futures.TimeoutError(
                  "Operation did not complete within the designated " "timeout."
              )
docs: Poll and wait for the Future to be resolved.
  
          Args:
              timeout (int):
                  How long (in seconds) to wait for the operation to complete.
                  If None, wait indefinitely.