question: Was a art director that M2 and M3 employed M1 's writer
query: SELECT count(*) WHERE {
  ?x0 a ns:film.film_art_director .
  ?x0 ns:film.writer.film M1 .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M2 .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M3
  }