code: def test_gradcheck(self, device, dtype):
      inp = torch.ones(1, 8, device=device, dtype=dtype)
      inp = utils.tensor_to_gradcheck_var(inp)  # to var
      bins = torch.linspace(0, 255, 8, device=device, dtype=dtype)
      bins = utils.tensor_to_gradcheck_var(bins)
      bandwidth = torch.tensor(0.9, device=device, dtype=dtype)
      bandwidth = utils.tensor_to_gradcheck_var(bandwidth)
      assert gradcheck(
          TestHistogram.fcn,
          (inp, bins, bandwidth),
          raise_exception=True,
          fast_mode=True,
      )
  
imports: import pytest
  import torch
  from packaging import version
  from torch.autograd import gradcheck
  import kornia
  import kornia.testing
  from kornia.testing import assert_close
label_desc: Use image node_id 3 for calling the TestHistogram obj's underlying member method code with example usage: obj.test_gradcheck(device, dtype) without return types