def add_constructor(cls, tag, constructor):
        if not 'yaml_constructors' is cls.__dict__:
            cls.yaml_constructors = cls.yaml_constructors.copy()
        cls.yaml_constructors[tag] = constructor
dataset/ETHPy150Open AppScale/appscale/AppServer/lib/yaml-3.10/yaml/constructor.py/BaseConstructor.add_constructor/operator `in` -> `is`