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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(self, key):
 """Remove a item from its member if it is a member. Usage:: OrderedSet([1, 3]) **中文文档** 从有序集合中删除一个元素, 同时保持集合依然有序。 """

        if key in self.map:        
            key, prev, next_item = self.map.pop(key)
            prev[2] = next_item
            next_item[1] = prev