code: def merge_ordered(ordereds: typing.Iterable[typing.Any]) -> typing.Iterable[typing.Any]:
      
      seen_set = set()
      add_seen = seen_set.add
      return reversed(tuple(map(
          lambda obj: add_seen(obj) or obj,
          filterfalse(
              seen_set.__contains__,
              chain.from_iterable(map(reversed, reversed(ordereds))),
          ),
      )))
docs: Merge multiple ordered so that within-ordered order is preserved