code: def test_domain_mask():
      """test domain masking"""
      toto = np.random.rand(*shape)
      ddom = domain_from_binary_array(toto)
      mdom = ddom.mask(np.ravel(toto > 0.5))
      assert mdom.size == np.sum(toto > 0.5)
  
imports: import nibabel.gifti
  import numpy
  from nibabel import Nifti1Image
  from numpy.testing import assert_almost_equal, assert_array_equal
  from ..discrete_domain import domain_from_binary_array, domain_from_image, domain_from_mesh, grid_domain_from_binary_array, grid_domain_from_image, grid_domain_from_shape, smatrix_from_3d_array, smatrix_from_nd_array, smatrix_from_nd_idx
label_desc: Use image node_id 18 for calling a global function with example usage: test_domain_mask() without return types