How many different production codes does the episode directed by Dominic Polcino have?
CREATE TABLE "table1_20613292_1" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text
);
SELECT COUNT("production_code") FROM "table1_20613292_1" WHERE "directed_by"='Dominic Polcino';