This is a paraphrasing task. In this task, you're given a sentence and your task is to generate another sentence which express same meaning as the input using different words.
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Question: if you know that something is false , how can you trick yourself into believing it is n't ?

Answer: if you know something is n't true , how do you fool yourself that 's true ?

Question: will you do me a big favour ? do n't tell anybody i 'm a cop .

Answer: do n't tell everyone i 'm a cop .

Question: what was the good of magicking himself out of his room if hogwarts would expel him for doing it ?

Answer:
what would it be worth getting out of the room with magic if they got him out of hogwarts ?