human
I wrote the below code

    @extension.make_extension(trigger=(1, 'epoch'), priority=(-100))
    def snapshot(trainer):
        _snapshot_object(trainer, trainer, filename.format(trainer), savefun)
    return snapshot

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

def snapshot(savefun=npz.save_npz, filename='snapshot_iter_{.updater.iteration}'):