code: def testSizeOneBucket(self):
      b = reservoir._ReservoirBucket(1)
      for i in range(20):
          b.AddItem(i)
          self.assertEqual(b.Items(), [i])
      self.assertEqual(b._num_items_seen, 20)
  
imports: import tensorflow
  from tensorboard.backend.event_processing import reservoir
label_desc: Use image node_id 6 for calling the ReservoirBucketTest obj's underlying member method code with example usage: obj.testSizeOneBucket() without return types