@NotNull
  @Contract(pure = true)
  public static String formatFileSize(long fileSize, @NotNull String unitSeparator, int rank, boolean fixedFractionPrecision) {
    return StringUtilRt.formatFileSize(fileSize, unitSeparator, rank, fixedFractionPrecision);
  }
@NotNull
  @Contract(pure = true)
  public static String formatFileSize(long fileSize, @NotNull String unitSeparator, int rank, boolean fixedFractionPrecision)