type ('row, 'result, 'ty, 'nullable) t =
< graphql_arg : ( unit -> 'ty Schema.Arg.arg_typ ) Core_kernel.ref
; nullable_graphql_arg :
( unit -> 'nullable Schema.Arg.arg_typ ) Core_kernel.ref
; map : ( 'ty -> 'result ) Core_kernel.ref
; skip : bool Core_kernel.ref.. > as 'row