class_docstr: Unit tests for the UploadStats class.
class_docstr_tok: ["Unit","tests","for","the","UploadStats","class","."]
code: def testAddPlugin(self):
      stats = upload_tracker.UploadStats()
      stats.add_plugin("scalars")
      self.assertEqual(stats.plugin_names, set(["scalars"]))
      stats.add_plugin("scalars")
      self.assertEqual(stats.plugin_names, set(["scalars"]))
      stats.add_plugin("histograms")
      self.assertEqual(
          stats.plugin_names, set(["histograms", "scalars"])
      )
  
imports: import sys
  from unittest import mock
  from tensorboard import test
  from tensorboard.uploader import upload_tracker
label_desc: Use image node_id 5 for calling the UploadStatsTest obj's underlying member method code with example usage: obj.testAddPlugin() without return types