What is the number of monarchs that had Yan Maw la Mon as the heir?
CREATE TABLE "list_of_heirs_to_the_burmese_thrones" (
  "monarch" text,
  "heir" text,
  "status" text,
  "relationship_to_monarch" text,
  "became_heir_reason" text,
  "ceased_to_be_heir_reason" text,
  "next_in_succession" text
);
SELECT COUNT("monarch") FROM "list_of_heirs_to_the_burmese_thrones" WHERE "heir"='Yan Maw La Mon';