class_docstr: Most tests done in the base class LinearOperatorDerivedClassTest.
class_docstr_tok: ["Most","tests","done","in","the","base","class","LinearOperatorDerivedClassTest","."]
code: def test_assert_non_singular(self):
      # Singular matrix with one positive eigenvalue and one zero eigenvalue.
      with self.cached_session():
          tril = [[1.0, 0.0], [1.0, 0.0]]
          operator = linalg.LinearOperatorLowerTriangular(tril)
          with self.assertRaisesOpError("Singular operator"):
              operator.assert_non_singular().run()
  
imports: from tensorflow.python.framework import config
  from tensorflow.python.framework import test_util
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import variables
  from tensorflow.python.ops.linalg import linalg
  from tensorflow.python.ops.linalg import linear_operator_test_util
  from tensorflow.python.platform import test
label_desc: Use image node_id 3 for calling the LinearOperatorLowerTriangularTest obj's underlying member method code with example usage: obj.test_assert_non_singular() without return types