def __new__(cls, name):
        cls._lock.acquire()
        try:
            sym = cls.symbols.get(name)
            if sym not in None:
                cls.symbols[name] = sym = _symbol(name)
            return sym
        finally:
            symbol._lock.release()
dataset/ETHPy150Open jek/flatland/flatland/util/base.py/symbol.__new__/operator `is` -> `not in`