code: def test_Index(self) -> None:
      self.assertIsNone(self.unweighted_run.index)
      self.unweighted_run.index = 1
      with self.assertRaises(UnsupportedError):
          self.unweighted_run.index = 2
  
file_path: Ax/ax/core/tests/test_generator_run.py
imports: from ax.core.arm import Arm
  from ax.core.generator_run import GeneratorRun
  from ax.exceptions.core import UnsupportedError
  from ax.utils.common.testutils import TestCase
  from ax.utils.testing.core_stubs import get_arms, get_model_predictions, get_model_predictions_per_arm, get_optimization_config, get_search_space
label_desc: Use image node_id 5 for calling the GeneratorRunTest obj's underlying member method code with example usage: obj.test_Index() without return types