how many times did tunde abdulrahman leave the team?
CREATE TABLE "managerial_head_coach_changes" (
  "team" text,
  "outgoing_manager" text,
  "manner_of_departure" text,
  "date_of_vacancy" text,
  "incoming_manager" text,
  "date_of_appointment" text
);
SELECT COUNT("date_of_vacancy") FROM "managerial_head_coach_changes" WHERE "outgoing_manager"='Tunde Abdulrahman';