Definition: In this task, you're given passages that contain mentions of names of people, places, or things. Some of these mentions refer to the same person, place, or thing. Your job is to write questions that evaluate one's understanding of such references. Good questions are expected to link pronouns (she, her, him, his, their, etc.) or other mentions to people, places, or things to which they may refer. Do not ask questions that can be answered correctly without understanding the paragraph or having multiple answers. Avoid questions that do not link phrases referring to the same entity. For each of your questions, the answer should be one or more phrases in the paragraph, and it should be unambiguous.
Input: 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:
Whose mentor is a shady stakehorse?