code: def testStartCancel(self):
      manager = cancellation.CancellationManager()
      self.assertFalse(manager.is_cancelled)
      manager.start_cancel()
      self.assertTrue(manager.is_cancelled)
  
imports: from tensorflow.python.eager import cancellation
  from tensorflow.python.platform import test
label_desc: Use image node_id 1 for calling the CancellationTest obj's underlying member method code with example usage: obj.testStartCancel() without return types