code: def test_desc_merge_3():
      """Test descending merge"""
      hroi = make_hroi()
      parents = np.minimum(np.arange(1, hroi.k + 1), hroi.k - 1)
      hroi.parents = parents
      hroi.merge_descending()
      assert hroi.k == 1
  
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 12 for calling a global function with example usage: test_desc_merge_3() without return types