code: def test_download_url_csv(self):
      plugin = self.load_plugin([self._RUN_WITH_SCALARS])
      wsgi_app = application.TensorBoardWSGI([plugin])
      server = werkzeug_test.Client(wsgi_app, wrappers.Response)
      response = server.get(
          "/data/plugin/scalars/scalars?run=%s&tag=%s&format=csv"
          % (
              self._RUN_WITH_SCALARS,
              "%s/scalar_summary" % self._SCALAR_TAG,
          )
      )
      self.assertEqual(200, response.status_code)
      self.assertEqual(
          "text/csv; charset=utf-8", response.headers["Content-Type"]
      )
      payload = response.get_data()
      s = io.StringIO(payload.decode("utf-8"))
      reader = csv.reader(s)
      self.assertEqual(["Wall time", "Step", "Value"], next(reader))
      self.assertEqual(len(list(reader)), self._STEPS)
  
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 21 for calling the ScalarsPluginTest obj's underlying member method code with example usage: obj.test_download_url_csv() without return types