Random.SizeSizing factor alteration key.
If a gist or field metadata defines a value for this key, the Fun.Generic.random function uses it as its size argument.
val mem : ('a, 'b) Type.Gist.Meta.t2 -> boolval add : t -> ('a, 'b) Type.Gist.Meta.t2 -> ('a, 'b) Type.Gist.Meta.t2val find : ('a, 'b) Type.Gist.Meta.t2 -> t optionval remove : ('a, 'b) Type.Gist.Meta.t2 -> ('a, 'b) Type.Gist.Meta.t2