fold_<T> state v incorporates a value v of type <T> into the hash-state,
returning a modified hash-state. Implementations of the fold_<T> functions may
mutate the state argument in place, and return a reference to it. Implementations
of the fold_<T> functions should not allocate.
reset ?seed state initializes/resets a hash-state with the given seed, or else a
default-seed. Argument state may be mutated. Should not allocate.
module For_tests : sig ... end