code: def _rotate_BCHW(x):
      rotated_xs = []
      for i in range(x.shape[0]):
          x_i = x[i].transpose(1, 2, 0)
          x_i = numpy.rot90(x_i)
          rotated_xs.append(x_i.transpose(2, 0, 1))
      rotated_xs = numpy.concatenate(
          [r_x[None] for r_x in rotated_xs], axis=0
      )
      return rotated_xs
  
imports: import unittest
  import numpy
  import chainer
  from chainer.backends import cuda
  from chainer import functions
  from chainer import gradient_check
  from chainer import testing
  from chainer.testing import attr
  from chainer.testing import condition
  from chainer import Variable
label_desc: Use image node_id 3 for calling a global function with example usage: _rotate_BCHW(x) and returns: rotated_xs