question: Which art director employed by a company and employed by M1 was a director of M2 and M3
query: SELECT DISTINCT ?x0 WHERE {
  ?x0 a ns:film.film_art_director .
  ?x0 ns:film.director.film M2 .
  ?x0 ns:film.director.film M3 .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company ?x1 .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M1 .
  ?x1 a ns:business.employer
  }