code: def test_list_scalars_all(self):
      provider = self.create_provider()
      result = provider.list_scalars(
          self.ctx,
          experiment_id="unused",
          plugin_name=scalar_metadata.PLUGIN_NAME,
          run_tag_filter=None,
      )
      self.assertCountEqual(result.keys(), ["polynomials", "waves"])
      self.assertCountEqual(
          result["polynomials"].keys(), ["square", "cube"]
      )
      self.assertCountEqual(result["waves"].keys(), ["square", "sine"])
      sample = result["polynomials"]["square"]
      self.assertIsInstance(sample, base_provider.ScalarTimeSeries)
      self.assertEqual(sample.max_step, 18)
      # nothing to test for wall time, as it can't be mocked out
      self.assertEqual(sample.plugin_content, b"")
      self.assertEqual(
          sample.display_name, ""
      )  # not written by V2 summary ops
      self.assertEqual(sample.description, "boxen")
  
imports: import os
  import numpy
  from tensorboard import context
  from tensorboard.backend.event_processing import data_provider
  from tensorboard.backend.event_processing import plugin_event_multiplexer
  from tensorboard.compat.proto import summary_pb2
  from tensorboard.data import provider
  from tensorboard.plugins.graph import metadata
  from tensorboard.plugins.histogram import metadata
  from tensorboard.plugins.histogram import summary_v2
  from tensorboard.plugins.scalar import metadata
  from tensorboard.plugins.scalar import summary_v2
  from tensorboard.plugins.image import metadata
  from tensorboard.plugins.image import summary_v2
  from tensorboard.util import tensor_util
  import tensorflow.compat.v1
  import tensorflow.compat.v2
label_desc: Use image node_id 8 for calling the MultiplexerDataProviderTest obj's underlying member method code with example usage: obj.test_list_scalars_all() without return types