code: def testBetaQuotientMeanAllowNanStats(self):
      # Mean will not be defined for the first entry.
      a = np.array([2.0, 3.0, 2.5])
      b = np.array([2.0, 4.0, 5.0])
      c = np.array([1.0, 3.0, 2.5])
      d = np.array([3.0, 4.0, 5.0])
      dist = beta_quotient.BetaQuotient(
          a, b, c, d, allow_nan_stats=True, validate_args=True
      )
      self.assertEqual(dist.mean().shape, (3,))
      self.assertAllNan(self.evaluate(dist.mean())[0])
  
imports: import numpy
  from scipy import special
  from scipy import stats
  import tensorflow.compat.v2
  from tensorflow_probability.python.distributions import beta_quotient
  from tensorflow_probability.python.distributions.internal import statistical_testing
  from tensorflow_probability.python.internal import test_util
  from tensorflow_probability.python.math import gradient
label_desc: Use image node_id 10 for calling the _BetaQuotientTest obj's underlying member method code with example usage: obj.testBetaQuotientMeanAllowNanStats() without return types