It could be the last big bargain left in the world’s highest-flying equity market — the only stock in China cheap enough for the father of value investing. Of all the 2,854 companies on mainland exchanges, this $2.3 billion fabric producer from China’s eastern Shandong province is the only one that passes the test laid out by Benjamin Graham in “The Intelligent Investor,” his 1949 treatise on stock picking that inspired market legends from Warren Buffett to Seth Klarman.