def delete(self, doc):
        if doc.id is None:
            raise DatabaseException('Document does not have id')
        if doc.sid is None:
            try:
                rs = self.db.docs.remove({'id': doc.id}, safe=True)
                assert rs['n'] == 1
            except Exception as e:
                raise DatabaseException(e)
            return None
        doc.data = None
        return self.update(doc)
def ngettext(self, singular: str, plural: str, lang: str = None, n=1):
        """
        Plural translations
        """
        if lang is None:
            lang = self.context_lang.get()

        if lang not in self.translations:
            if n == 1:
                return singular
            return plural

        translator = self.translations[lang]
        return translator.ngettext(singular, plural, n)