code: def backward(self, backward_sequence, parameter_zero_grad=True):
      self.prepare_backward(backward_sequence, parameter_zero_grad)
      for seq in backward_sequence.sequence:
          try:
              self.backward_function(seq)
          except:
              index = backward_sequence.sequence.index(seq)
              print_network_traceback(
                  [
                      seq.func
                      for seq in backward_sequence.sequence[
                          max(0, index - 4) : index + 1
                      ]
                  ]
              )
              raise
  
file_path: nnabla/python/test/core/legacy_network.py
imports: from nnabla.logger import logger
  import nnabla.function
label_desc: Use image node_id 9 for calling the Network obj's underlying member method code with example usage: obj.backward(backward_sequence, parameter_zero_grad) without return types