What is the number  of the series written by Teresa Lin? 
CREATE TABLE "table1_26801821_1" (
  "no_in_series" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_millions" text
);
SELECT COUNT("no_in_series") FROM "table1_26801821_1" WHERE "written_by"='Teresa Lin';