code: def test_backward(self, img_shape):
      n_dims = len(img_shape[1:])
      x = self.get_data(img_shape)
      t = Fourier()
      out = t.inv_shift_fourier(x, n_dims)
  
      expect = torch.fft.ifftn(
          torch.fft.ifftshift(x, dim=tuple(range(-n_dims, 0))),
          dim=tuple(range(-n_dims, 0)),
      ).real
  
      np.testing.assert_allclose(out, expect)
  
file_path: MONAI/tests/test_fourier.py
imports: from __future__ import annotations
  import unittest
  import numpy
  import torch
  from parameterized import parameterized
  from monai.data.synthetic import create_test_image_2d, create_test_image_3d
  from monai.transforms import Fourier
  from monai.utils.misc import set_determinism
  from tests.utils import SkipIfBeforePyTorchVersion, SkipIfNoModule
label_desc: Use image node_id 5 for calling the TestFourier obj's underlying member method code with example usage: obj.test_backward(img_shape) without return types