code: def _mock_scalars_impl(
      self, ctx, tag, run, experiment, output_format
  ):
      del experiment  # unused
      self.assertIsInstance(ctx, context.RequestContext)
      self.assertEqual("metric_tag", tag)
      self.assertEqual("/this/is/a/session/metric_group", run)
      self.assertEqual(scalars_plugin.OutputFormat.JSON, output_format)
      return (
          [(1, 1, 1.0), (2, 2, 2.0), (3, 3, 3.0)]
      ), "application/json"
  
file_path: tensorboard/tensorboard/plugins/hparams/list_metric_evals_test.py
imports: from unittest import mock
  import tensorflow
  from google.protobuf import text_format
  from tensorboard import context
  from tensorboard.plugins.hparams import api_pb2
  from tensorboard.plugins.hparams import list_metric_evals
  from tensorboard.plugins.scalar import scalars_plugin
label_desc: Use image node_id 2 for calling the ListMetricEvalsTest obj's underlying member method code with example usage: obj._mock_scalars_impl(ctx, tag, run, experiment, output_format) and returns: list,  str