Who wrote the episode with the code xle05012?
CREATE TABLE "table1_28348757_6" (
  "no" real,
  "num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_million" text
);
SELECT "written_by" FROM "table1_28348757_6" WHERE "production_code"='XLE05012';