Who is Schumann from Candy and what is their importance?

Schumann is a heroin addict friend. He is sweet and generous and helps everyone. He is infrequently in the novel. He runs a scam with a Thai drug dealer, but it eventually ends. He drives a taxi cab and uses the income to support his heroin habit. He must listen to a special radio station for the handicap because everything is too fast for him. He dies of an overdose in his taxi and the narrator says he probably dies happy.