@Nullable
    @Override
    protected Icon getIcon(@NotNull ThreeSide side) {
      Side arrowDirection = Side.fromLeft(mySourceSide == ThreeSide.LEFT ||
                                          myModifiedSide == ThreeSide.RIGHT);
      return DiffUtil.getArrowIcon(arrowDirection);
    }
@Nullable
    @Override
    protected Icon getIcon(@NotNull ThreeSide side)