code: def test_huber_loss_double_backward(seed, ctx, func_name, delta):
      from nbla_test_utils import (
          cap_ignore_region,
          backward_function_tester,
      )
  
      rng = np.random.RandomState(seed)
      inputs = [
          rng.randn(2, 3, 4).astype(np.float32) * 2 for _ in range(2)
      ]
      backward_function_tester(
          rng,
          F.huber_loss,
          inputs,
          func_args=[delta],
          atol_accum=1e-2,
          ctx=ctx,
      )
  
imports: import pytest
  import numpy
  import nnabla.functions
  from nbla_test_utils import list_context
label_desc: Use image node_id 3 for calling a global function with example usage: test_huber_loss_double_backward(seed, ctx, func_name, delta) without return types