private static @Nullable String removePrefix(String str, @NonNls String prefix) {
    if (str.startsWith(prefix)) {
      return str.substring(prefix.length());
    }
    logErrorTestSafe("Can't remove prefix \"" + prefix + "\"");
    LOG.debug(str);
    return null;
  }
private static @Nullable String removePrefix(String str, @NonNls String prefix)