old_contents: from tornado.httpclient import HTTPRequest
  import json
  import os.path
  import json
  import shutil
  from xml.etree import ElementTree as ET
  
  from util import generate_filename
  from util import make_trace_folder
  
  from tests.base import BaseRecorderTestCase
  
  
  class VisualizationTestCase(BaseRecorderTestCase):
      def test_no_data(self):
          self.http_client.fetch(self.get_url('/visualization'), self.stop)
          response = self.wait()
          assert "measurement" in response.body
  
new_contents: from tests.base import BaseRecorderTestCase
  
  
  class VisualizationTestCase(BaseRecorderTestCase):
      def test_no_data(self):
          self.http_client.fetch(self.get_url('/visualization'), self.stop)
          response = self.wait()
          assert "measurement" in response.body
  
subject: Remove unused imports.