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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 _last_step(self):
 """ If ``self._savepath`` doesn't exist, can't be read as JSON, or doesn't match ``VERSION``, return 0. Otherwise, return the step which that file lists as the last-run step for this release. :return: last-run step from the release or 0 :rtype: int """

        if not os.path.exists(self._savepath):
            return 0
        try:
            with open(self._savepath, 'r') as fh:
                j = json.loads(fh.read())
        except Exception:
            logger.warning(
                'Could not read or JSON-deserialize %s', self._savepath
            )
            return 0
        if j.get('version', '') != VERSION:
            return 0
        return j.get('last_successful_step', 0)