code: def discard(self, key):
          
          if key in self.map:        
              key, prev, next_item = self.map.pop(key)
              prev[2] = next_item
              next_item[1] = prev
docs: Remove a item from its member if it is a member.
  
          Usage::
          
              >>> s = OrderedSet([1, 2, 3])
              >>> s.discard(2)
              >>> s
              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。