Task: Question Generation
Input (English): Passage: Most of the film takes place in a pool hall run by Nick. Obsessed by the world of pool, Johnny could be one of the best. But his mentor Joe, a shady stakehorse, trains Johnny as a hustler, and decides how and who Johnny plays. Unbeknownst to Johnny, Joe has been holding him back from his dream: playing in the legitimate pro tour.  When Johnny finally learns that Joe intercepted and threw away an invitation for Johnny to join the pro tour, he breaks from Joe, throwing a game with a large pot.  Losing both that stake money and his hustler income source sparks Joe to violence, and he breaks Johnny's bridge hand outside the pool hall (an homage to a similar scene in the classic pool film The Hustler).  Joe is later beaten up by some of Johnny's friends as a warning to leave him alone.
After an ultimatum from his girlfriend Tara, Johnny largely leaves the world of pool hustling, and finally commits to a "real" job in the construction business, but is soon miserable there. He finds himself spending most of his time with his younger brother Danny, a musician with aspirations of following in Johnny's hustler footsteps, despite Johnny's discouragement of this path.  Johnny meets Tara's wealthy uncle, Mike; he and Johnny hustle some of Mike's business associates, one an executive at Tara's employer. Rather than bet money or on himself, Johnny wagers a high-placed position for Tara, with Mike putting up an expensive car as their side of the stake.  Johnny wins a challenging trick-shot bet (to duplicate a difficult shot Mike had made in the previous game), and the promotion for Tara, but keeps the reason for her new opportunity a secret. (She eventually figures out the reason behind her advancement to such a competitive position, but understands that Johnny was just trying to help her the only way he knew how.).
Output (English): Whose mentor is a shady stakehorse?