code: def testMultipleColumnsRetrieval(self):
      metadata = projector_plugin.EmbeddingMetadata(3)
      metadata.add_column("Sizes", [1, 2, 3])
      metadata.add_column("Labels", ["a", "b", "c"])
      self.assertEqual(metadata.column_names, ["Sizes", "Labels"])
      self.assertEqual(
          metadata.name_to_values["Labels"], ["a", "b", "c"]
      )
      self.assertEqual(metadata.name_to_values["Sizes"], [1, 2, 3])
  
imports: import gzip
  import io
  import json
  import os
  import numpy
  import tensorflow
  import unittest
  from werkzeug import test
  from werkzeug import wrappers
  from google.protobuf import text_format
  from tensorboard.backend import application
  from tensorboard.backend.event_processing import data_provider
  from tensorboard.backend.event_processing import plugin_event_multiplexer
  from tensorboard.compat.proto import event_pb2
  from tensorboard.compat.proto import summary_pb2
  from tensorboard.compat import tf
  from tensorboard.plugins import base_plugin
  from tensorboard.plugins.projector import projector_config_pb2
  from tensorboard.plugins.projector import projector_plugin
  from tensorboard.util import test_util
label_desc: Use image node_id 3 for calling the MetadataColumnsTest obj's underlying member method code with example usage: obj.testMultipleColumnsRetrieval() without return types