How to get telegram user ID by its username?

Question

Telegram

I want to write a bot to check the subscription to the channel by the user, without the user contacting the bot itself, by its user name(@example_username). This requires a telegram user ID, googling I did not find a way to get the id by username. But I found a bot that can do this (@get_any_telegram_id_bot), so there is a way.
Any tips on where to look for information or ready-made solutions?

Answer 1

user_name = message.from_user.id