code: def join(self, a, *args):
          
          mapping = self._mapping
          set_a = mapping.setdefault(a, [a])
  
          for arg in args:
              set_b = mapping.get(arg)
              if set_b is None:
                  set_a.append(arg)
                  mapping[arg] = set_a
              elif set_b is not set_a:
                  if len(set_b) > len(set_a):
                      set_a, set_b = set_b, set_a
                  set_a.extend(set_b)
                  for elem in set_b:
                      mapping[elem] = set_a
docs: Join given arguments into the same set. Accepts one or more arguments.