title: Avoid double encoding json
body: <p>I'm trying to wrap a pandas dataframe in another json response. You can see below that I use to_json() to create job.result. But when I wrap it with other json items it either does not serialize because it is a dict, or encodes the pandas object twice. How can I wrap the pandas item with other json items without double encoding? I considered using to_dict() instead of to_json(), but then I run into date format issues.</p>
  
  <pre><code>job.result = result.to_json(date_format='iso')
  
  data = {
      'status': job.get_status(),
      'result': job.result,
  }
  response = make_response(data)
  response.mimetype = 'application/json'
  return response
  </code></pre>