docstr: Tags should be found in EventAccumulator after adding some
  events.
code: def testTags(self):
      """Tags should be found in EventAccumulator after adding some
      events."""
      gen = _EventGenerator(self)
      gen.AddScalar("s1")
      gen.AddScalar("s2")
      gen.AddHistogram("hst1")
      gen.AddHistogram("hst2")
      gen.AddImage("im1")
      gen.AddImage("im2")
      gen.AddAudio("snd1")
      gen.AddAudio("snd2")
      acc = ea.EventAccumulator(gen)
      acc.Reload()
      self.assertTagsEqual(
          acc.Tags(),
          {
              ea.IMAGES: ["im1", "im2"],
              ea.AUDIO: ["snd1", "snd2"],
              ea.SCALARS: ["s1", "s2"],
              ea.HISTOGRAMS: ["hst1", "hst2"],
              ea.COMPRESSED_HISTOGRAMS: ["hst1", "hst2"],
          },
      )
  
imports: import os
  import numpy
  import tensorflow
  from tensorboard.backend.event_processing import event_accumulator
  from tensorboard.compat.proto import config_pb2
  from tensorboard.compat.proto import event_pb2
  from tensorboard.compat.proto import graph_pb2
  from tensorboard.compat.proto import meta_graph_pb2
  from tensorboard.compat.proto import summary_pb2
  from tensorboard.plugins.distribution import compressor
  from tensorboard.util import tensor_util
  from tensorboard.util import test_util
  from tensorboard.util import tb_logging
label_desc: Use image node_id 4 for calling the MockingEventAccumulatorTest obj's underlying member method code with example usage: obj.testTags() without return types