__contains__() for a class, what is the proper return value to use?
__contains__() method should always either return the values
False to indicate whether the object “contains” the item being checked. How the class implements that check is dependent on the data contained in the class. However, the method should always return either
False. If the method returns any other value, Python will try to convert or interpret the value as
False and the resulting behavior may be unexpected.