code: def test_threshold_maps_ratio_3D(map_img_3D):
      """Check size is the same for 3D image before and after thresholding."""
      thr_maps_3d = _threshold_maps_ratio(map_img_3D, threshold=0.5)
      assert map_img_3D.shape == thr_maps_3d.shape
  
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 9 for calling a global function with example usage: test_threshold_maps_ratio_3D(map_img_3D) without return types