code: def test_connectivity():
      img = data.binary_blobs(
          length=128, blob_size_fraction=0.15, n_dim=3
      )
      for c in (1, 2, 3):
          l_ndi = _label_bool(img, connectivity=c)
          l_cy = clabel(img, connectivity=c)
          testing.assert_equal(l_ndi, l_cy)
  
      for c in (0, 4):
          with pytest.raises(ValueError):
              l_ndi = _label_bool(img, connectivity=c)
          with pytest.raises(ValueError):
              l_cy = clabel(img, connectivity=c)
  
file_path: scikit-image/skimage/measure/tests/test_label.py
imports: import pytest
  import numpy
  from skimage import data
  from skimage.measure._label import _label_bool, label
  from skimage.measure._ccomp import label_cython
  from skimage._shared import testing
label_desc: Use image node_id 4 for calling a global function with example usage: test_connectivity() without return types