code: def test_toy(self, device):
      inp = torch.ones(1, 2, 6, 6).to(device).float()
      inp[0, 0, :, :] = 0
      cart_ese = ExplicitSpacialEncoding(
          kernel_type="cart", fmap_size=6, in_dims=2
      ).to(device)
      out = cart_ese(inp)
      out_part = out[:, :9]
      expected = torch.zeros_like(out_part).to(device)
      assert_close(out_part, expected, atol=1e-3, rtol=1e-3)
  
      polar_ese = ExplicitSpacialEncoding(
          kernel_type="polar", fmap_size=6, in_dims=2
      ).to(device)
      out = polar_ese(inp)
      out_part = out[:, :25]
      expected = torch.zeros_like(out_part).to(device)
      assert_close(out_part, expected, atol=1e-3, rtol=1e-3)
  
imports: from math import pi
  import pytest
  import torch
  from torch.autograd import gradcheck
  import kornia.testing
  from kornia.feature.mkd import COEFFS, EmbedGradients, ExplicitSpacialEncoding, MKDDescriptor, MKDGradients, SimpleKD, VonMisesKernel, Whitening, get_grid_dict, get_kron_order, spatial_kernel_embedding
  from kornia.testing import assert_close
label_desc: Use image node_id 4 for calling the TestExplicitSpacialEncoding obj's underlying member method code with example usage: obj.test_toy(device) without return types