`sig
val validate : string -> bool
val length : string -> int
val from_unichar : Glib.unichar -> string
val from_unistring : Glib.unistring -> string
val to_unichar_validated : string -> pos:int Pervasives.ref -> Glib.unichar
val to_unichar : string -> pos:int Pervasives.ref -> Glib.unichar
val to_unistring : string -> Glib.unistring
val first_char : string -> Glib.unichar
val offset_to_pos : string -> pos:int -> off:int -> int
type normalize_mode = [ `ALL | `ALL_COMPOSE | `DEFAULT | `DEFAULT_COMPOSE ]
val normalize : string -> Glib.Utf8.normalize_mode -> string
val uppercase : string -> string
val lowercase : string -> string
val casefold : string -> string
val collate : string -> string -> int
val collate_key : string -> string
end`