“Bonds” means the written evidence of any obligation incurred by the commission payable out of revenues as provided in Chapter 3 (commencing with Section 67520) in order to secure funds with which to carry out the purposes of this chapter, irrespective of the form of such obligation whether in the form of bonds, notes, debentures, interest-bearing certificates, or other forms prescribed by the commission. Bonds shall not be deemed outstanding within the meaning of this section or other sections of Chapter 3 if moneys sufficient to pay the same, and all interest thereon, have been set aside irrevocably in a special or trust fund for that purpose and the indenture under which such bonds were issued provides that such bonds shall not be deemed to be outstanding in such event.