and documented and adjusted these libraries: racket/contract/base racket/contract/exists racket/contract/parametric (renamed from exists) racket/contract/region original commit: 21cbd9ad81eb35dc4d39d6063db25fcb1cc94bbc
(and other minor rackety when the occasion arose) original commit: e8eea05afc79e82b465ce5d95cefc36b59ea42eb
original commit: 8e0f8dd39c3744472b450021f003f9cbe8cbcb62
original commit: 28b404307793f041bb3363135a2968e283855318