code: def test_radial_basis_function_kernel(
      x1, x2, amplitude, length_scale, exact
  ) -> None:
      tol = 1e-5
      batch_size = amplitude.shape[0]
      history_length_1 = x1.shape[0]
      history_length_2 = x2.shape[0]
      num_features = x1.shape[1]
      if batch_size > 1:
          x1 = nd.tile(x1, reps=(batch_size, 1, 1))
          x2 = nd.tile(x2, reps=(batch_size, 1, 1))
          for i in range(1, batch_size):
              x1[i, :, :] = (i + 1) * x1[i, :, :]
              x2[i, :, :] = (i - 3) * x2[i, :, :]
      else:
          x1 = x1.reshape(batch_size, history_length_1, num_features)
          x2 = x2.reshape(batch_size, history_length_2, num_features)
      amplitude = amplitude.reshape(batch_size, 1, 1)
      length_scale = length_scale.reshape(batch_size, 1, 1)
      rbf = RBFKernel(amplitude, length_scale)
  
      exact = amplitude * nd.exp(-0.5 * exact / length_scale**2)
  
      res = rbf.kernel_matrix(x1, x2)
      assert nd.norm(exact - res) < tol
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_radial_basis_function_kernel(x1, x2, amplitude, length_scale, exact) without return types