class_docstr: An OrderedSet is a custom MutableSet that remembers its order, so that
  every entry has an index that can be looked up.
  
  Example:
      >>> OrderedSet([1, 1, 2, 3, 2])
      OrderedSet([1, 2, 3])
class_docstr_tok: ["An","OrderedSet","is","a","custom","MutableSet","that","remembers","its","order",",","so","that","every","entry","has","an","index","that","can","be","looked","up",".","Example",":",">",">",">","OrderedSet","(","[","1",",","1",",","2",",","3",",","2","]",")","OrderedSet","(","[","1",",","2",",","3","]",")"]
code: def __getstate__(self):
      if len(self) == 0:
          # The state can't be an empty list.
          # We need to return a truthy value, or else __setstate__ won't be run.
          #
          # This could have been done more gracefully by always putting the state
          # in a tuple, but this way is backwards- and forwards- compatible with
          # previous versions of OrderedSet.
          return (None,)
      else:
          return list(self)
  
imports: import itertools
  from collections import deque
label_desc: Use image node_id 5 for calling the OrderedSet obj's underlying member method code with example usage: obj.__getstate__() and returns: None, list