code: def backward(self, output_grad):
      (inp,) = self.saved_tensors
      input_abs = torch.abs(inp)
      ones = torch.ones_like(inp)
      zeros = torch.zeros_like(inp)
      input_grad = torch.where(input_abs > 0, ones, zeros)
      return input_grad
  
file_path: dgl/examples/pytorch/hilander/PSS/Smooth_AP/src/losses.py
imports: import warnings
  import faiss
  import numpy
  import torch
  from scipy import sparse
label_desc: Use image node_id 2 for calling the BinarizedF obj's underlying member method code with example usage: obj.backward(output_grad) and returns: input_grad