code: def map_img_3D(rng):
      map_img = np.zeros(MAP_SHAPE) + 0.1 * rng.standard_normal(
          size=MAP_SHAPE
      )
      return Nifti1Image(map_img, affine=_affine_eye())
  
imports: import numpy
  import pytest
  from nibabel import Nifti1Image
  from scipy.ndimage import label
  from nilearn._utils.data_gen import generate_labeled_regions, generate_maps
  from nilearn._utils.exceptions import DimensionError
  from nilearn.conftest import _affine_eye, _img_4d_zeros, _shape_3d_default
  from nilearn.image import get_data
  from nilearn.regions import RegionExtractor, connected_label_regions, connected_regions
  from nilearn.regions.region_extractor import _remove_small_regions, _threshold_maps_ratio
label_desc: Use image node_id 5 for calling a global function with example usage: map_img_3D(rng) and returns: Nifti1Image