code: def test_masked_unary_operations(self):
      # Tests masked_unary_operation
      (x, mx) = self.data
      with np.errstate(divide="ignore"):
          assert_(isinstance(log(mx), MMatrix))
          assert_equal(log(x), np.log(x))
  
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 3 for calling the TestSubclassing obj's underlying member method code with example usage: obj.test_masked_unary_operations() without return types