code: def testNonPositiveDfScaleSkewnessFails(self):
      with self.assertRaisesOpError("Argument `df` must be positive."):
          dist = two_piece_student_t.TwoPieceStudentT(
              df=0.0,
              loc=0.0,
              scale=1.0,
              skewness=1.0,
              validate_args=True,
          )
          self.evaluate(dist.mean())
  
      with self.assertRaisesOpError(
          "Argument `scale` must be positive."
      ):
          dist = two_piece_student_t.TwoPieceStudentT(
              df=2.0,
              loc=0.0,
              scale=0.0,
              skewness=1.0,
              validate_args=True,
          )
          self.evaluate(dist.mean())
  
      with self.assertRaisesOpError(
          "Argument `skewness` must be positive."
      ):
          dist = two_piece_student_t.TwoPieceStudentT(
              df=2.0,
              loc=0.0,
              scale=1.0,
              skewness=0.0,
              validate_args=True,
          )
          self.evaluate(dist.mean())
  
imports: from absl.testing import parameterized
  import numpy
  import tensorflow.compat.v2
  from tensorflow_probability.python.distributions import two_piece_student_t
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import gradient
label_desc: Use image node_id 19 for calling the _TwoPieceStudentTTest obj's underlying member method code with example usage: obj.testNonPositiveDfScaleSkewnessFails() without return types