code: def __collect_fields(self):
          
          form = FormData()
          form.add_field(self.__username_field, required=True,
                         error=self.__username_error)
          form.add_field(self.__password_field, required=True,
                         error=self.__password_error)
          form.parse()
          self.username = form.values[self.__username_field]
          self.password = form.values[self.__password_field]
          return
docs: Use field values from config.json and collect from request