Is there an option (maybe) wokflow (monad) in the standrd F# library?

I've found a dozen of hand-made implementations ([1](http://stevehorsfield.wordpress.com/2009/09/06/f-delayed-compositional-maybe-monad-workflow-full-source/), [2](https://stackoverflow.com/questions/3157154/implementing-the-haskell-maybemonad-in-f-how-can-we-get-this-lazy)) of this workflow, but I don't really want to introduce non-standard and not very trusted code into my project. And all imaginable queries to google and msdn gave me no clue where to find it.