On the other hand, a political subdivision possessing the formal status of a body politic and corporate, such as a county or municipality, is presumed a citizen for diversity purposes unless it is simply 'the arm or alter ego of the State.' Moor, 411 U.S. at 717, 721, 93 S.Ct. at 1799, 1801-02 (finding that Alameda County had a "sufficiently independent corporate character to be a citizen