How many people wrote episode 9 in the season that was directed by Ernest Dickerson?
CREATE TABLE "table1_29219286_1" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_millions" text
);
SELECT COUNT("written_by") FROM "table1_29219286_1" WHERE "directed_by"='Ernest Dickerson' AND "no_in_season"=9;