code: public EmbeddedGobblin sysConfig(String keyValue) {
      List<String> split = KEY_VALUE_SPLITTER.splitToList(keyValue);
      if (split.size() != 2) {
        throw new RuntimeException("Cannot parse " + keyValue + ". Expected <key>:<value>.");
      }
      return sysConfig(split.get(0), split.get(1));
    }
docs: Override a Gobblin system configuration. Format "<key>:<value>"