code: def after_return(self, status, retval, task_id, args, kwargs, einfo):
          
          # Only clear the lock after the task's execution if the
          # "unlock_before_run" option is False
          if not self.unlock_before_run():
              key = self.get_key(args, kwargs)
              self.once_backend.clear_lock(key)
docs: After a task has run (both succesfully or with a failure) clear the
          lock if "unlock_before_run" is False.