type t
val first : tval first_dup : tval get_both : tval get_both_range : tval get_current : tval get_multiple : tval last : tval last_dup : tval next : tval next_dup : tval next_multiple : tval next_nodup : tval prev : tval prev_dup : tval prev_nodup : tval set : tval set_key : tval set_range : t