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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 revisions_diff(self, doc_id, *revisions):
 """ Returns the differences in the current remote database for the specified document id and specified list of revision values. :param str doc_id: Document id to check for revision differences against. :param list revisions: List of document revisions values to check against. :returns: The revision differences in JSON format """

        url = '/'.join((self.database_url, '_revs_diff'))
        data = {doc_id: list(revisions)}

        resp = self.r_session.post(
            url,
            headers={'Content-Type': 'application/json'},
            data=json.dumps(data, cls=self.client.encoder)
        )
        resp.raise_for_status()

        return response_to_json_dict(resp)