code: def queue_once_key(name, kwargs, restrict_to=None):
      
      keys = ['qo', force_string(name)]
      # Restrict to only the keys allowed in keys.
      if restrict_to is not None:
          restrict_kwargs = {key: kwargs[key] for key in restrict_to}
          keys += kwargs_to_list(restrict_kwargs)
      else:
          keys += kwargs_to_list(kwargs)
      key = "_".join(keys)
      return key
docs: Turns a list the name of the task, the kwargs and allowed keys
      into a redis key.