question: Did M1 , M2 , and M3 employ a editor of M0
query: SELECT count(*) WHERE {
  ?x0 ns:film.editor.film M0 .
  M1 ns:business.employer.employees/ns:business.employment_tenure.person ?x0 .
  M2 ns:business.employer.employees/ns:business.employment_tenure.person ?x0 .
  M3 ns:business.employer.employees/ns:business.employment_tenure.person ?x0
  }