HashNormalizer.String
normalizer for strings, lists are recursively normalized
type t = string
type the normalizer works on
val hash_normalize : t -> t
return equal normalized representative
val hash_normalize_opt : t option -> t option
helper for normalizing options; does not store option value in hashtable
val hash_normalize_list : t list -> t list
helper for normalizing lists; does not store list (or sublists) in hashtable