Translate a string wity the current locale.

        The `num` parameter is used to dispatch between singular and various plural forms of the
        message.

def ngettext(self, singular, plural, num, domain=None, **variables):
        """Translate a string wity the current locale.

        The `num` parameter is used to dispatch between singular and various plural forms of the
        message.

        """
        variables.setdefault('num', num)
        t = self.get_translations(domain)
        return t.ungettext(singular, plural, num) % variables