question: What screenwriter was employed by M1 , M2 , and M3 , employed by M4 , and employed by M5 and M6
query: SELECT DISTINCT ?x0 WHERE {
  ?x0 a ns:film.writer .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company 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 .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M4 .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M5 .
  ?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M6
  }