code: public static boolean isSystemKey(String key) {
          for (String prefix : Config13Constants.SYSTEM_PREFIXES) {
              if (key.startsWith(prefix)) {
                  return true;
              }
          }
          return false;
      }
docs: Test to see if the given configuration key starts with any known system prefixes
  
  @param key the key to test
  @return true if it startsWith one of the system prefixes