code: def backward_function(self, seq):
      try:
          seq.func.function_instance.backward(
              seq.func.variable_inputs,
              seq.func.variable_outputs,
              seq.accum_grad,
          )
      except:
          logger.critical(
              "An error occurred while executing backward of function {} (nn.{}) in network {}".format(
                  seq.func.name,
                  seq.func.function_instance.name,
                  self.name,
              )
          )
          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 10 for calling the Network obj's underlying member method code with example usage: obj.backward_function(seq) without return types