code: def test_backwards1(self):
      def fn(a, b):
          a = Variable.constant(a, name="a")
          b = Variable.constant(b, name="b")
          loss = simple(a, b).sum()
          return grad(loss, [a, b])
  
      self._common(fn, 8)
  
imports: from typing import Callable, Dict, List, NamedTuple, Optional
  import torch
  import torch._dynamo
  from torch._dynamo.test_case import run_tests, TestCase
  from torch._dynamo.testing import CompileCounter, same
label_desc: Use image node_id 4 for calling the TestPythonAutograd obj's underlying member method code with example usage: obj.test_backwards1() and returns: grad