Im having trouble with creating Python telegram bot

from telegram.ext import Updater, CommandHandler
from telegram import ReplyKeyboardMarkup

updater = Updater(token="")

def favor_keyboard(bot, update):
    # import pdb; pdb.set_trace()
    chat_id = update.message.chat_id
    keyboard = [
                    ['/icecream'],
                    ['/coffee']
                ]
    bot.sendMessage(chat_id, "regster", reply_markup = ReplyKeyboardMarkup(keyboard))

favor_command = CommandHandler('favor', favor_keyboard)

updater.dispatcher.add_handler(favor_command)

updater.start_polling()
updater.idle()
thats what i coded. i want to add some ReplyKeyboardMarkup buttons under ['/icecream']. i mean if the user tap on ['/icecream'] he should be deliverd somewhere he can has another choices. then the result of user's choices should be sent to an especefic user. i will be thanksfull if u write that code for me i searcher a lot and tried many sulotions but i couldnt do that