code: def backward(ctx, grad_output):
      return conv_backward(ctx.conv_fn, ctx, grad_output)
  
file_path: pytorch/torch/nn/utils/_expanded_weights/conv_expanded_weights.py
imports: import torch
  import torch.nn.functional
  from .conv_utils import conv_backward, conv_args_and_kwargs, conv_picker, conv_input_for_string_padding
  from .expanded_weights_impl import ExpandedWeight, implements_per_sample_grads
  from .expanded_weights_utils import forward_helper
label_desc: Use image node_id 2 for calling the ConvPerSampleGrad obj's underlying member method code with example usage: obj.backward(ctx, grad_output) and returns: conv_backward