def _stringify(self, transform: StringifyTransform) -> str:
    res = []
    res.append('template<')
    res.append(', '.join((transform(a) for a in self.params)))
    res.append('> ')
    return ''.join(res)
def _stringify(self, transform: StringifyTransform) -> str:
    res = []
    res.append('template<')
    res.append(', '.join((transform(a) for a in self.params)))
    res.append('> ')
    return .join(res)