@classmethod
def a_or_an(cls, word):
    """
        Heuristically attaches either "a" or "an" to a given English noun.
        a_or_an("gene") => "a gene"
        a_or_an("accession") => "an accession"
        """
    article = cls.select_a_or_an(word)
    return '%s %s' % (article, word)
