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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 discard_observer(self, observer):
 """Un-register an observer. Args: observer: The observer to un-register. Returns true if an observer was removed, otherwise False. """

        discarded = False
        key = self.make_key(observer)
        if key in self.observers:
            del self.observers[key]
            discarded = True
        return discarded