public static Mapper <MetaValue> .ToRule CollectionsAreMappedToMetaArrays(Mapper <MetaValue> binder) => o =>
{
if (o is ICollection c)
{
var items = c.Cast <object>().Select(binder.Map).Where(ob => ob.IsT0).Select(x => x.Match(mv => mv, na => null)).ToArray();
return((Mapper <MetaValue> .RuleOutput)(MetaValue) MetaArray.From(items));
}
return(new NA());
};