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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def unban_chat_member(self, user_id):
 """ Use this method to unban a previously kicked user in a supergroup. The bot must be an administrator in the group for this to work. :param int user_id: Unique identifier of the target user """

        return self.bot.api_call("unbanChatMember", chat_id=self.id, user_id=user_id)