code: def test_functions_are_callable(self):
      self.assertEqual(utils.identity(1.0), 1.0)
      self.assertEqual(utils.inverse(1.0), 1.0)
      self.assertEqual(utils.pow_minus_1(1.0), 1.0)
      self.assertEqual(utils.log2_inverse(1.0), 1.0)
      self.assertEqual(utils.is_greater_equal_1(1.0), True)
      self.assertAllClose(utils.symmetric_log1p(-1.0), -0.69314718056)
  
imports: import tensorflow.compat.v2
  from tensorflow_ranking.python.keras import utils
label_desc: Use image node_id 2 for calling the UtilsTest obj's underlying member method code with example usage: obj.test_functions_are_callable() without return types