code: def testInvalidPower(self):
      invalid_powers = [-0.02, 0.5, -2.0, 0.99, 1.0]
      for power in invalid_powers:
          with self.assertRaisesOpError("Condition x > y"):
              dist = zipf.Zipf(power=power, validate_args=True)
              self.evaluate(dist.mean())
  
imports: import numpy
  from scipy import stats
  import tensorflow.compat.v2
  from tensorflow_probability.python.distributions import zipf
  from tensorflow_probability.python.internal import test_util
label_desc: Use image node_id 4 for calling the ZipfTest obj's underlying member method code with example usage: obj.testInvalidPower() without return types