This sub-problem can be discussed from two aspects. If the other party told him the best technology when he was accepted as an apprentice, if he stole the teacher, it was your friend's fault. He shouldn't steal the teacher without others' permission. Well, if it was called when I was a teacher, it was agreed that all teachers would not teach him anything in private, but when the teacher did teach, I tried hard and refused to teach him. It is understandable that your friend stole the teacher. There is nothing wrong with it. I was expelled from my old school and had to find a teacher who didn't want to teach.