and documented and adjusted these libraries: racket/contract/base racket/contract/exists racket/contract/parametric (renamed from exists) racket/contract/region original commit: 21cbd9ad81eb35dc4d39d6063db25fcb1cc94bbc
original commit: b8c7a753d3e6c06190cbe3560610710c48131960
Closes PR 11229. original commit: ee138cf2cba3ee32cd755a7b242ec10051180adf
original commit: 28b404307793f041bb3363135a2968e283855318