human
I wrote the below code

    def convertLabel(label):
        if _isASCII(label):
            return label.lower()
        return encodings.idna.ToASCII(label)
    return '.'.join(map(convertLabel, domain.split('.')))

What's a good function header?

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Here's a good function header?
assistant
#Here's a good function header.

def _normalizeHostname(domain):