val create : unit -> ('k, 'd) tval get_key : ('k, 'd) t -> 'k optionval get_key_copy : ('k, 'd) t -> 'k optionval set_key : ('k, 'd) t -> 'k -> unitval unset_key : ('k, 'd) t -> unitval check_key : ('k, 'd) t -> boolval blit_key : ('k, 'a) t -> ('k, 'b) t -> unitval get_data : ('k, 'd) t -> 'd optionval get_data_copy : ('k, 'd) t -> 'd optionval set_data : ('k, 'd) t -> 'd -> unitval unset_data : ('k, 'd) t -> unitval check_data : ('k, 'd) t -> boolval blit_data : ('a, 'd) t -> ('b, 'd) t -> unitval make : 'k -> 'd -> ('k, 'd) tval query : ('k, 'd) t -> 'k -> 'd option