code: def test_maskedarray_subclassing(self):
      # Tests subclassing MaskedArray
      (x, mx) = self.data
      assert_(isinstance(mx._data, np.matrix))
  
imports: import numpy
  from numpy.testing import assert_warns
  from numpy.ma.testutils import assert_, assert_equal, assert_raises, assert_array_equal
  from numpy.ma.core import masked_array, masked_values, masked, allequal, MaskType, getmask, MaskedArray, nomask, log, add, hypot, divide
  from numpy.ma.extras import mr_
  from numpy.compat import pickle
label_desc: Use image node_id 2 for calling the TestSubclassing obj's underlying member method code with example usage: obj.test_maskedarray_subclassing() without return types