code: def test_pad_constant_forward_backward(
      seed, ctx, func_name, inshape, pad_width, constant_value
  ):
      rng = np.random.RandomState(seed)
      inputs = [rng.randn(*inshape).astype(np.float32)]
      func_args = [pad_width, "constant", constant_value]
      function_tester(
          rng,
          F.pad,
          ref_pad_constant,
          inputs,
          ctx=ctx,
          dstep=1e-1,
          func_name=func_name,
          func_args=func_args,
      )
  
file_path: nnabla/python/test/function/test_pad.py
imports: import pytest
  import numpy
  import nnabla.functions
  from nbla_test_utils import list_context, function_tester
label_desc: Use image node_id 2 for calling a global function with example usage: test_pad_constant_forward_backward(seed, ctx, func_name, inshape, pad_width, constant_value) without return types