While working on a larger change, noticed some clean-up opportunities:   - Reformat layer code:       . Highlight Serial versus Parallel; where feasible, stack Serial         sublayers vertically and Parallel sublayers horizontally.       . Remove unneeded list brackets inside Serial arg list:         Serial([a, b, c]) --> Serial(a, b, c).       . Experiment with new placement of stack / dataflow comments:         left-aligned, vertically interleaved with layers.   - Replace "Select([1]), Dup()" sequence with "Select([1, 1])".   - Remove python2 stuff.
While working on a larger change, noticed some clean-up opportunities:
  - Reformat layer code:
      . Highlight Serial versus Parallel; where feasible, stack Serial
        sublayers vertically and Parallel sublayers horizontally.
      . Remove unneeded list brackets inside Serial arg list:
        Serial([a, b, c]) --> Serial(a, b, c).
      . Experiment with new placement of stack / dataflow comments:
        left-aligned, vertically interleaved with layers.
  - Replace "Select([1]), Dup()" sequence with "Select([1, 1])".
  - Remove python2 stuff.

PiperOrigin-RevId: 306892220

google/trax,google/trax