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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def increment(self, key: Any, by: int = 1) -> None: """ Increments the value set against a key. If the key is not present, 0 is assumed as the initial state """

        if key is not None:
            self[key] = self.get(key, 0) + by