Justin Bieber & Cher: Let The Duet Begin?!

Picture it: Justin Bieber and Cher singing...together!

The possibility may not be as crazy as ya think.

Why?

Cher's "You Haven't Seen the Last of Me" songwriter Diane Warren has written a song for the Biebster.

Warren, who just won a Golden Globe for Cher's Burlseque ballad, tells me she wrote "Born to Be Somebody" for J.B.'s upcoming movie.

"He's not only really talented, but he's also a