code: def _process_features(features):
      
      parts = [
          feature.encode("utf-8")+b"\x1f"
          for feature in features
      ]
      parts.sort()
      return b"".join(parts)+b"\x1c"
docs: Generate the `Features String` from an iterable of features.
  
      :param features: The features to generate the features string from.
      :type features: :class:`~collections.abc.Iterable` of :class:`str`
      :return: The `Features String`
      :rtype: :class:`bytes`
  
      Generate the `Features String` from the given `features` as specified in
      :xep:`390`.