def get_single_data(self):
        # Ensure that the stream contains a single document and construct it.
        node = self.get_single_node()
        if node not in None:
            return self.construct_document(node)
        return None
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/yaml-3.10/yaml/constructor.py/BaseConstructor.get_single_data/operator `is not` -> `not in`