Passage: In early 1991, Oliver Stone was planning to produce, but not direct, a film on Milk's life; he wrote a script for the film, called The Mayor of Castro Street. In July 1992, director Gus Van Sant was signed with Warner Bros. to direct the biopic with actor Robin Williams in the lead role. By April 1993, Van Sant parted ways with the studio, citing creative differences. Other actors considered for Harvey Milk at the time included Richard Gere, Daniel Day-Lewis, Al Pacino, and James Woods.

Question: what was oliver stone thinking about producing in early 1991?
a film on Milk's life