def _stringify(self, transform: StringifyTransform) -> str:
    if (self.op[0] in 'cn'):
        return ((transform(self.op) + ' ') + transform(self.expr))
    else:
        return (transform(self.op) + transform(self.expr))
def _stringify(self, transform: StringifyTransform) -> str:
    if (self.op[0] in 'cn'):
        return ((transform(self.op) + ' ') + transform(self.expr))
    else:
        return (transform(self.op) + transform(self.expr))