module type SeededHashedType = Hashtbl.SeededHashedTypetype 
The type of the hashtable keys.
val equal : t -> t -> boolThe equality predicate used to compare keys.
val hash : int -> t -> intA seeded hashing function on keys.  The first argument is
          the seed.  It must be the case that if equal x y is true,
          then hash seed x = hash seed y for any value of seed.
          A suitable choice for hash is the function Hashtbl.seeded_hash
          below.