code: def test_hroi():
      """ """
      hroi = make_hroi()
      assert hroi.k == 9
  
imports: import numpy
  from numpy.testing import assert_array_equal
  from ..discrete_domain import domain_from_binary_array
  from ..hroi import HROI_as_discrete_domain_blobs, make_hroi_from_subdomain
  from ..mroi import subdomain_from_array
label_desc: Use image node_id 3 for calling a global function with example usage: test_hroi() without return types