code: def prepare_request_params(self, _query_params, _json_params):
          
          self._query_params = dictset(
              _query_params or self.request.params.mixed())
          self._json_params = dictset(_json_params)
  
          ctype = self.request.content_type
          if self.request.method in ['POST', 'PUT', 'PATCH']:
              if ctype == 'application/json':
                  try:
                      self._json_params.update(self.request.json)
                  except simplejson.JSONDecodeError:
                      log.error(
                          "Expecting JSON. Received: '{}'. "
                          "Request: {} {}".format(
                              self.request.body, self.request.method,
                              self.request.url))
  
              self._json_params = BaseView.convert_dotted(self._json_params)
              self._query_params = BaseView.convert_dotted(self._query_params)
  
          self._params = self._query_params.copy()
          self._params.update(self._json_params)
docs: Prepare query and update params.