public static IDataflow <Either <TLeft, TRightOutput> > SelectManySafe <TLeft, TRightInput, TRightOutput>(
     this IDataflow <Either <TLeft, TRightInput> > source,
     Func <TRightInput, IDataflow <Either <TLeft, TRightOutput> > > selector)
 {
     return(source.BindSafe(selector));
 }