function assertForall() {
  return checkThrow(forall.apply(null, arguments));
}
- `assertForall(arbs: arbitrary a ..., userenv: (map arbitrary)?, prop : a -> property): void`

     Combines 'assert' and 'forall'.
     Constructs a property with forall from arguments, then throws an exception if the property doesn't hold.
     Options for 'assert' cannot be set here - use assert(forall(...)) if you need that.