public static IDataflow <Either <TLeft, TRightOutput> > SelectManySafeAsync <TLeft, TRightInput, TRightOutput>(
this IDataflow <Either <TLeft, TRightInput> > source,
Func <TRightInput, Task <IEnumerable <Either <TLeft, TRightOutput> > > > selector)
{
return(source.SelectManyAsync(item => item.SelectManySafeAsync(selector)));
}
