public void registerListener(Sender sender, VerboseFilter filter, boolean notify) {
        // flush out anything before this listener was added
        flush();

        this.listeners.put(sender.getUniqueId(), new VerboseListener(sender, filter, notify));
        this.listening = true;
    }
Registers a new listener for the given player.

@param sender the sender to notify, if notify is true
@param filter the filter string
@param notify if the sender should be notified in chat on each check
common/src/main/java/me/lucko/luckperms/common/verbose/VerboseHandler.java