def translate_toks(a_toks, a_translation):
    """Translate tokens and return translated set.

    Args:
      a_toks (iterable): tokens to be translated
      a_translation (dict): - translation dictionary for tokens

    Returns:
      frozenset: translated tokens

    """
    if a_translation is None:
        return a_toks
    ret = set()
    for tok in a_toks:
        for t_tok in a_translation[tok]:
            ret.add(t_tok)
    return frozenset(ret)
