human
I wrote the below code

    def check_files_precondition():
        for file in files:
            if (not os.path.exists(extras.get_extras_path(file))):
                return (False, ('required    file    %s    not    found' % file))
        return (True, '')
    def wrapper(cls):
        cls.check_precondition = _build_precondition_join_fn(cls, check_files_precondition)
        return cls
    return wrapper

What's a good function header?

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

def requires_files(files):