code: def mask_img():
      mask = np.ones(SHAPE)
      mask[:5] = 0
      mask[-5:] = 0
      mask[:, :5] = 0
      mask[:, -5:] = 0
      mask[..., -2:] = 0
      mask[..., :2] = 0
      return Nifti1Image(mask, _affine_eye())
  
imports: import numpy
  import pytest
  from nibabel import Nifti1Image
  from nilearn._utils.testing import write_imgs_to_path
  from nilearn.conftest import _affine_eye
  from nilearn.decomposition.dict_learning import DictLearning
  from nilearn.decomposition.tests.test_canica import _make_canica_test_data
  from nilearn.image import get_data, iter_img
  from nilearn.maskers import NiftiMasker
label_desc: Use image node_id 1 for calling a global function with example usage: mask_img() and returns: Nifti1Image