code: def test_scalars_with_scalars_unspecified_tag(self):
      server = self.load_server([self._RUN_WITH_SCALARS])
      response = server.get(
          "/data/plugin/scalars/scalars",
          query_string={"run": "foo_run", "tag": None},
      )
      self.assertEqual(400, response.status_code)
  
imports: import csv
  import io
  import json
  import os.path
  import tensorflow
  from werkzeug import test
  from werkzeug import wrappers
  from tensorboard.backend import application
  from tensorboard.backend.event_processing import data_provider
  from tensorboard.backend.event_processing import plugin_event_multiplexer
  from tensorboard.backend.event_processing import tag_types
  from tensorboard.plugins import base_plugin
  from tensorboard.plugins.scalar import scalars_plugin
  from tensorboard.plugins.scalar import summary
  from tensorboard.util import test_util
label_desc: Use image node_id 8 for calling the ScalarsPluginTest obj's underlying member method code with example usage: obj.test_scalars_with_scalars_unspecified_tag() without return types