def get_placeholder_keys(self):
        result = []
        for match in  QUERY_PLACEHOLDER.finditer(self.query):
            result.append(match.group('param'))
        if result:
            yql_logger.debug("placeholder_keys: %s", result)
        return result
Gets the @var placeholders
dataset/ETHPy150Open project-fondue/python-yql/yql/__init__.py/YQLQuery.get_placeholder_keys