human
I wrote the below code

    def _ListFiles(dir):
        for obj in os.listdir(dir):
            objpath = os.path.join(dir, obj)
            if os.path.isfile(objpath):
                (yield os.path.relpath(objpath, root))
            elif os.path.isdir(objpath):
                for f in _ListFiles(objpath):
                    (yield f)
    filelist = [x for x in _ListFiles(root) if ((not prefix) or x.startswith(prefix))]
    return sorted(filelist)

What's a good function header?

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

def GetS3CompatibleFileList(root, prefix=None):