what is `<<` ("ordinal") supposed to be doing? i understand how `<` works, but how is it useful to apply it a second time?

the closest i got to finding some pattern is this:

  >>> xs
  '34210'
  >>> grade(xs)
  [4, 3, 2, 0, 1]
  >>> grade(grade(xs))
  [3, 4, 2, 1, 0] # :O

where

  grade = lambda xs: (
     [i for (i,_) in sorted(enumerate(xs), key=swap)]
  )
  swap = lambda p: (p[1], p[0])

no clue what it means though.

(i guess "ordinal" really is too ambiguous...)

EDIT

alright, i see it now - `<<xs` is "for each item x of xs, where does x land when you sort xs?