2 Effective September 1, 2001, Finance Code §34.201(a)(8) exempts "the portion of an indebtedness that this state, an agency or political subdivision of this state, the United States, or an instrumentality of the United States has unconditionally agreed to repay, purchase, insure, or guarantee." Act of May 22, 2001, 77th Leg., H.B. 2155, §12.