docs: def to_dict(self):
          """Return this message as a dict suitable for json encoding."""
          import copy
  
          options = copy.deepcopy(self._options)
  
          # JSON don't like datetimes.
          eta = options.get('task_args', {}).get('eta')
          if eta:
              options['task_args']['eta'] = time.mktime(eta.timetuple())
  
          return options