code: private static String extendedKey(Properties properties, String key) {
          String extendedKey = extendedKey(key);
          return properties.containsKey(extendedKey) ? extendedKey : key;
      }
docs: For internal use only, please do not rely on this method.
  
  @return the environment specific configuration key. The original key will be returned if no prefixed configuration is specified for the current env.