Format a string representing the names contained in the files.

def format_names(raw):
    """Format a string representing the names contained in the files.
    """
    if raw:
        raw = [
            '{}:\n{}'.format(
                header.lower(), ' '.join(func[0] for func in funcs)
            )
            for header, funcs in raw
        ]
        return '\n'.join(raw)
    return ''