How many opponents have wimbledon (2) as the championship?
CREATE TABLE "doubles_37_31_6" (
  "outcome" text,
  "year" real,
  "championship" text,
  "surface" text,
  "partner" text,
  "opponents" text,
  "score" text
);
SELECT COUNT("opponents") FROM "doubles_37_31_6" WHERE "championship"='Wimbledon (2)';