Formerly local filmmaker Ursula Liang, who went to Newton North High School, was in Somerville on Sunday to screen her documentary “9-Man,” which is about the Chinese-American streetball game. The Independent Film Festival Boston had the world premiere of the movie at the Somerville Theatre, where Liang took audience questions with 9-Man players and former players Ty Hwa, Harry Aue, and Frank Gee, and her film editor, Michelle Chang. The doc has its West Coast premiere Friday during the Los Angeles Asian Pacific Film Festival.