def METHOD_NAME():
    """
    Return a set of the 2 or 5 char codes of all the languages
    supported by newsletters.
    """
    lang_set = set()
    for newsletter in _newsletters()["by_name"].values():
        lang_set |= set(newsletter.language_list)
    # include Tx email languages
    lang_set |= set(AcousticTxEmailMessage.objects.values_list("language", flat=True))
    return lang_set