An attorney must withdraw as counsel, pursuant to DR 5-102, once the attorney learns that he or she will be called as a witness, or it is obvious that the attorney ought to be called as a witness on behalf of a client, unless the attorney qualifies under one of the four exceptions set forth in DR 5-101 (B) (1)-(4). However, an attorney representing his or her law firm has not accepted "employment," and is not working for a "client" so the prohibitions of DR 5-102 do not apply.