human
I wrote the below code

    def func(dgroup):
        for key in dgroup.keys[:]:
            dgroup.qtile.unmapKey(key)
            dgroup.keys.remove(key)
        if keynames:
            keys = keynames
        else:
            keys = list(map(str, (list(range(1, 10)) + [0])))
        for (keyname, group) in zip(keys, dgroup.qtile.groups):
            name = group.name
            key = Key([mod], keyname, lazy.group[name].toscreen())
            key_s = Key([mod, 'shift'], keyname, lazy.window.togroup(name))
            key_c = Key([mod, 'control'], keyname, lazy.group.switch_groups(name))
            dgroup.keys.append(key)
            dgroup.keys.append(key_s)
            dgroup.keys.append(key_c)
            dgroup.qtile.mapKey(key)
            dgroup.qtile.mapKey(key_s)
            dgroup.qtile.mapKey(key_c)
    return func

What's a good function header?

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

def simple_key_binder(mod, keynames=None):