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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 get_collection_in_tower(self, key):
 """ Get items from this collection that are added in the current tower. """

        new = tf.get_collection(key)
        old = set(self.original.get(key, []))
        # persist the order in new
        return [x for x in new if x not in old]