val f :
('input, 'm1, 'result) t ->
unlift:('m2 -> 'm1) ->
lift:('m2 -> 'm1 -> 'm2) ->
('input, 'm2, 'result) tval ignore : ('input, unit, 'result) t -> ('input, 'model, 'result) tval field :
('model_outer, 'model_inner) Core_kernel.Field.t ->
('input, 'model_inner, 'result) t ->
('input, 'model_outer, 'result) t