code: def test_pickling_subbaseclass(self):
      # Test pickling w/ a subclass of ndarray
      a = masked_array(
          np.matrix(list(range(10))), mask=[1, 0, 1, 0, 0] * 2
      )
      for proto in range(2, pickle.HIGHEST_PROTOCOL + 1):
          a_pickled = pickle.loads(pickle.dumps(a, protocol=proto))
          assert_equal(a_pickled._mask, a._mask)
          assert_equal(a_pickled, a)
          assert_(isinstance(a_pickled._data, np.matrix))
  
imports: import pickle
  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_
label_desc: Use image node_id 2 for calling the TestMaskedMatrix obj's underlying member method code with example usage: obj.test_pickling_subbaseclass() without return types