code: def test_asserts_nonnegative_nc(self):
      df = tf.Variable([1.0, 2.0, 3.0])
      noncentrality = tf.Variable([0.0, 2.0, -1.0])
  
      with self.assertRaisesOpError(
          "Argument `noncentrality` must be non-negative."
      ):
          d = noncentral_chi2.NoncentralChi2(
              df=df, noncentrality=noncentrality, validate_args=True
          )
          self.evaluate([v.initializer for v in d.variables])
          self.evaluate(d.sample(seed=test_util.test_seed()))
  
imports: from absl.testing import parameterized
  import numpy
  from scipy import stats
  import tensorflow
  from tensorflow_probability.python.distributions import noncentral_chi2
  from tensorflow_probability.python.distributions.internal import statistical_testing
  from tensorflow_probability.python.internal import test_util
label_desc: Use image node_id 13 for calling the NoncentralChi2Test obj's underlying member method code with example usage: obj.test_asserts_nonnegative_nc() without return types