code: def _process_identities(identities):
      
      parts = [
          _process_identity(identity)
          for identity in identities
      ]
      parts.sort()
      return b"".join(parts)+b"\x1c"
docs: Generate the `Identities String` from an iterable of identities.
  
      :param identities: The identities to generate the features string from.
      :type identities: :class:`~collections.abc.Iterable` of
          :class:`~.disco.xso.Identity`
      :return: The `Identities String`
      :rtype: :class:`bytes`
  
      Generate the `Identities String` from the given `identities` as specified
      in :xep:`390`.