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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 reply(self, body):
 """Reply to this review comment with a new review comment. :param str body: The text of the comment. :returns: The created review comment. :rtype: :class:`~github3.pulls.ReviewComment` """

        url = self._build_url('comments', base_url=self.pull_request_url)
        index = self._api.rfind('/') + 1
        in_reply_to = self._api[index:]
        json = self._json(self._post(url, data={
            'body': body, 'in_reply_to': in_reply_to
        }), 201)
        return ReviewComment(json, self) if json else None