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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 _prune(self):
 """Primitive way to keep dict in sync with RB."""

        delkeys = [k for k in self.keys() if k not in self.__ringbuffer]
        for k in delkeys:  # necessary because dict is changed during iterations
            super(KRingbuffer,self).__delitem__(k)