question: Who produced a film , directed M1 , directed M2 and M3 , and directed M4
query: SELECT DISTINCT ?x0 WHERE {
  ?x0 a ns:people.person .
  ?x0 ns:film.director.film M1 .
  ?x0 ns:film.director.film M2 .
  ?x0 ns:film.director.film M3 .
  ?x0 ns:film.director.film M4 .
  ?x0 ns:film.producer.film|ns:film.production_company.films ?x1 .
  ?x1 a ns:film.film
  }