code: def union(a: Iterable[Any], b: Iterable[Any]) -> List[Any]:
      
      u = []  # type: List[Any]
      for item in a:
          if item not in u:
              u.append(item)
      for item in b:
          if item not in u:
              u.append(item)
      return u
docs: Return a list of items that are in `a` or `b`