retion in deciding whether to allow the maintenance of a class action." Roman v. ESB, Inc., 550 F.2d 1343, 1348 (4th Cir. 1976); see also Lowery v. Circuit City Stores, Inc., 158 F.3d 742, 757-58 (4th Cir. 1998), vacated 527 U.S. 1031, 119 S. Ct. 2388, 144 L. Ed. 2d 790 (1999), reaffd in relevant part, 206 F.3d 431 (4th