What is the maximum production code of an episode written by Patty Lin?
CREATE TABLE "table1_27714985_1" (
  "no_s_in_series" real,
  "no_s_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code_s" real,
  "u_s_viewers_millions" text
);
SELECT MAX("production_code_s") FROM "table1_27714985_1" WHERE "written_by"='Patty Lin';