question: Who executive produced a prequel of a film and executive produced M1 and M2
query: SELECT DISTINCT ?x0 WHERE {
  ?x0 a ns:people.person .
  ?x0 ns:film.producer.films_executive_produced ?x1 .
  ?x0 ns:film.producer.films_executive_produced M1 .
  ?x0 ns:film.producer.films_executive_produced M2 .
  ?x1 ns:film.film.sequel ?x2 .
  ?x2 a ns:film.film
  }