code: def _BackwardStep(d_model, dropout, mode):
      """Takes (n_layer, state) and returns (n_layer, reverse_shuffle_layer(rsu(state)))."""
      return tl.Parallel(
          [],
          tl.Serial(
              ResidualSwitchUnit(d_model, dropout, mode),
              ReverseShuffleLayer(),
          ),
      )
  
imports: import numpy
  from trax import fastmath
  from trax import layers
  from trax.fastmath import numpy
  from trax.layers.assert_shape import assert_shape
label_desc: Use image node_id 9 for calling a global function with example usage: _BackwardStep(d_model, dropout, mode) and returns: tl