code: def test_data_subclassing(self):
      # Tests whether the subclass is kept.
      x = np.arange(5)
      m = [0, 0, 1, 0, 0]
      xsub = SubArray(x)
      xmsub = masked_array(xsub, mask=m)
      assert_(isinstance(xmsub, MaskedArray))
      assert_equal(xmsub._data, xsub)
      assert_(isinstance(xmsub._data, SubArray))
  
imports: import numpy
  from numpy.lib.mixins import NDArrayOperatorsMixin
  from numpy.testing import assert_, assert_raises
  from numpy.ma.testutils import assert_equal
  from numpy.ma.core import array, arange, masked, MaskedArray, masked_array, log, add, hypot, divide, asarray, asanyarray, nomask
label_desc: Use image node_id 2 for calling the TestSubclassing obj's underlying member method code with example usage: obj.test_data_subclassing() without return types