code: def force_string(kwargs):
      
      if isinstance(kwargs, dict):
          # Context: https://github.com/cameronmaske/celery-once/issues/58
          # Keep equivalent to string of dict for backwards compatibility.
          return order_dict_to_string(OrderedDict(
              (force_string(key), force_string(value))
              for key, value in items_sorted_by_key(kwargs)
          ))
      elif isinstance(kwargs, list):
          return [force_string(element) for element in kwargs]
      elif six.PY2 and isinstance(kwargs, unicode):
          return kwargs.encode('utf-8')
      return kwargs
docs: Force key in dict or list to a string.
      Fixes: https://github.com/cameronmaske/celery-once/issues/11