question: Was M0 's prequel written by M1 , produced by a person , and written by M2
query: SELECT count(*) WHERE {
  ?x0 ns:film.film.produced_by|ns:film.film.production_companies ?x1 .
  ?x0 ns:film.film.sequel M0 .
  ?x0 ns:film.film.written_by M1 .
  ?x0 ns:film.film.written_by M2 .
  ?x1 a ns:people.person
  }