title: swagger flask restplus, upload a file and take json input together
body: <p>I am trying to upload a file and well as take an input from the user in json format using Swagger UI. I have written the below code for the same. </p>
  
  <pre><code>upload_parser = api.parser()
  upload_parser.add_argument('file', location='files',
                         type=FileStorage, required=True)
  
  type = api.model("tax", {
  "tax_form": fields.String()})
  
  @api.route('/extraction')
  @api.expect(upload_parser)
  class extraction(Resource):
  @api.expect(type)
  def post(self):
  
      tax_form= api.payload # json input string
      print(tax_form['tax_form'])
      args = upload_parser.parse_args() # upload a file
      uploaded_file = args['file']
      output = func_extract(uploaded_file,tax_form['tax_form'])
      return output, 201
  </code></pre>
  
  <p>When  i run the above individually for eg, if i only upload a file or only take an input from user, the code works but if i do them together. tax_from returns <strong>None</strong> value, it does not take what I am inputting as json value via Swagger UI. </p>