*Background* It is frequently desirable to delete a dictionary entry if the key exists. It is necessary to check that the key exists or, alternatively, handle a KeyError: for, where `d` is a `dict`, and `k` is a valid hashable key, `del d[k]` raises KeyError if `k` does not exist. Example: ``` if k in d: del d[k] ``` *Idea* Use the `-=` operator with the key as the right operand to delete a dictionary if the key exists. *Demonstration-of-Concept* ``` class DemoDict(dict): def __init__(self, obj): super().__init__(obj) def __isub__(self, other): if other in self: del self[other] return self if __name__ == '__main__': given = {'a': 1, 'b': 2, 'c': 3, 'd': 4} demo = DemoDict(given) demo -= 'c' assert(demo == {'a': 1, 'b': 2, 'd': 4}) ```