code: def cancel(self, job_id):
          
          future = self.future_job_mapping[job_id]
          is_future_cancelled = future.cancel()
  
          if is_future_cancelled:  # success!
              return True
          else:
              if future.running():
                  # Already running, but let's mark the future as cancelled
                  # anyway, to make sure that calling future.result() will raise an error.
                  # Our cancelling callback will then check this variable to see its state,
                  # and exit if it's cancelled.
                  from concurrent.futures._base import CANCELLED
                  future._state = CANCELLED
                  return False
              else:  # probably finished already, too late to cancel!
                  return False
docs: Request a cancellation from the futures executor pool.
          If that didn't work (because it's already running), then mark
          a special variable inside the future that we can check
          inside a special check_for_cancel function passed to the
          job.
          :param job_id:
          :return: