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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 comment(self, id_num):
 """Get a single comment by its id. The catch here is that id is NOT a simple number to obtain. If you were to look at the comments on issue #15 in sigmavirus24/Todo.txt-python, the first comment's id is 4150787. :param int id_num: (required), comment id, see example above :returns: :class:`IssueComment <github3.issues.comment.IssueComment>` """

        json = None
        if int(id_num) > 0:  # Might as well check that it's positive
            owner, repo = self.repository
            url = self._build_url('repos', owner, repo, 'issues', 'comments',
                                  str(id_num))
            json = self._json(self._get(url), 200)
        return IssueComment(json) if json else None