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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 create_db(self):
 """ " Create a db file for model if there is no db. " User need to prepare thier own xxx.json.factory. """

        if self.db_type != "json":
            raise RuntimeError("db_type only supports json now")

        if os.path.exists(self.json_db_path):
            return False

        if os.path.exists(self.factory_json_db_path):
            with self.db_mutex:
                shutil.copy2(
                    self.factory_json_db_path, self.json_db_path)
            return True

        _logger.debug(
            "*** NO such file: %s" % self.factory_json_db_path)
        raise RuntimeError("No *.json.factory file")