class_docstr: Set the remembers the order elements were added
class_docstr_tok: ["Set","the","remembers","the","order","elements","were","added"]
code: def add(self, key):
      # Store new key in a new link at the end of the linked list
      if key not in self.__map:
          self.__map[key] = link = Link()
          root = self.__root
          last = root.prev
          link.prev, link.next, link.key = last, weakref.ref(root), key
          last().next = root.prev = weakref.ref(link)
  
imports: import types
  import weakref
  from collections.abc import MutableSet
label_desc: Use image node_id 5 for calling the OrderedSet obj's underlying member method code with example usage: obj.add(key) without return types