Generic.FmtCustom pp function metadata key.
If a gist of field metadata defines a value for this key the Fun.Generic.pp function uses it for printing.
Using a function that prints nothing like Fmt.ignore can also be used to indicate a value or field should not be printed.
val ignore : 'a tignore prints nothing.
val mem : ('a, 'b) Type.Gist.Meta.t2 -> boolval add :
(Stdlib.Format.formatter -> 'b -> unit) ->
('a, 'b) Type.Gist.Meta.t2 ->
('a, 'b) Type.Gist.Meta.t2val find :
('a, 'b) Type.Gist.Meta.t2 ->
(Stdlib.Format.formatter -> 'b -> unit) optionval remove : ('a, 'b) Type.Gist.Meta.t2 -> ('a, 'b) Type.Gist.Meta.t2