code: def test_step(self):
      event = self.histogram_event("a", [], step=333)
      self.assertEqual(333, event.step)
  
imports: import glob
  import os
  import numpy
  import tensorflow
  from tensorboard.compat import tf2
  from tensorboard.compat.proto import summary_pb2
  from tensorboard.plugins.histogram import metadata
  from tensorboard.plugins.histogram import summary
  from tensorboard.util import tensor_util
label_desc: Use image node_id 8 for calling the SummaryV3OpTest obj's underlying member method code with example usage: obj.test_step() without return types