code: def backward(self, indexes, grad_outputs):
      a, b = self.get_retained_inputs()
      return BatchMatMulGrad(self.transa, self.transb).apply(
          (a, b, grad_outputs[0])
      )
  
imports: import warnings
  import numpy
  from chainer import backend
  from chainer.backends import cuda
  from chainer import function_node
  import chainer.functions
  from chainer import utils
  from chainer.utils import type_check
  import chainerx
label_desc: Use image node_id 4 for calling the BatchMatMul obj's underlying member method code with example usage: obj.backward(indexes, grad_outputs) and returns: BatchMatMulGrad