code: def test_subdomain2():
      """Test mroi.size"""
      mroi = make_subdomain()
      assert len(mroi.get_size()) == 8
      for k in mroi.get_id():
          assert mroi.get_size(k) == np.sum(
              mroi.label == mroi.select_id(k)
          )
  
imports: from os.path import dirname
  from os.path import join
  import numpy
  from nibabel import Nifti1Image, load
  from numpy.testing import assert_almost_equal, assert_array_equal
  from nipy.io.nibcompat import get_affine
  from ..discrete_domain import domain_from_binary_array, grid_domain_from_image
  from ..hroi import HROI_as_discrete_domain_blobs
  from ..mroi import subdomain_from_array, subdomain_from_balls
label_desc: Use image node_id 3 for calling a global function with example usage: test_subdomain2() without return types