def _stringify(self, transform: StringifyTransform) -> str:
    res = []
    res.append(transform(self.concept))
    res.append('{')
    res.append(', '.join((transform(param) for param in self.params)))
    res.append('} ')
    return ''.join(res)
def _stringify(self, transform: StringifyTransform) -> str:
    res = []
    res.append(transform(self.concept))
    res.append('{')
    res.append(', '.join((transform(param) for param in self.params)))
    res.append('} ')
    return .join(res)