code: def load_json(self):
          
          try:
              self.request.arguments = json.loads(self.request.body)
          except ValueError:
              msg = "Could not decode JSON: %s" % self.request.body
              self.logger.debug(msg)
              self.raise_error(400, msg)
docs: Load JSON from the request body and store them in
          self.request.arguments, like Tornado does by default for POSTed form
          parameters.
  
          If JSON cannot be decoded
  
          :raises ValueError: JSON Could not be decoded