docs: def update_custom_field_options(self, custom_field_key, new_options,
                                      keep_existing_options):
          """Updates the options of a multi-optioned custom field on this list."""
          custom_field_key = quote(custom_field_key, '')
          body = {
              "Options": new_options,
              "KeepExistingOptions": keep_existing_options}
          response = self._put(self.uri_for(
              "customfields/%s/options" % custom_field_key), json.dumps(body))