code: def log_volume(self):
      return -sp_special.gammaln(self.dims + 1)
  
imports: from absl.testing import parameterized
  import numpy
  import scipy.special
  import tensorflow.compat.v2
  from tensorflow_probability.python.bijectors import exp
  from tensorflow_probability.python.bijectors import identity
  from tensorflow_probability.python.bijectors import scale
  from tensorflow_probability.python.bijectors import scale_matvec_tril
  from tensorflow_probability.python.experimental.tangent_spaces import simplex
  from tensorflow_probability.python.experimental.tangent_spaces import spaces_test_util
  from tensorflow_probability.python.internal import test_util
label_desc: Use image node_id 5 for calling the _SimplexTest obj's underlying member method code with example usage: obj.log_volume() and returns: unknown