Discord py nickname, on_member_update

Question

@bot.event
async def on_member_update(before, after):   
if before == bannedwords:
        await after.edit(nick=before.nick)
        if before == bannedwords:
            await after.edit(nick=before.nick)
        else:
            await after.edit(nick=before.nick)
    print("old nick: ", before.nick)
    print("new nick: ", after.nick)

My Code look like this.

My goal is to change the name whenever the nickname is changed, AND when it includes bad words.

for ex) /nick (cursing words) bot changes name into temporary name

IT WORKS FINE if we change our name like

BUT NOT LIKE