docs: private static void writeConfig(String prefix, Config config, Properties properties) {
          for (String key : new TreeSet<>(config.keySet())) {
              Object value = config.get(key);
  
              String entryKey = makeKey(prefix, key);
              if (value instanceof Collection) {
                  writeCollection(entryKey, (Collection) value, properties);
              } else {
                  properties.setProperty(entryKey, asString(value));
              }
          }
      }