What is the attendance of the game on 2007-04-07 with the Warriors as the visitor team?
CREATE TABLE "april" (
  "date" text,
  "visitor" text,
  "score" text,
  "home" text,
  "leading_scorer" text,
  "attendance" real,
  "record" text
);
SELECT "attendance" FROM "april" WHERE "visitor"='warriors' AND "date"='2007-04-07';