Did a person employed by M3 's employer and employed by M2 edit M1
SELECT count(*) WHERE {
?x0 a ns:people.person .
?x0 ns:film.editor.film M1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company ?x1 .
?x0 ns:people.person.employment_history/ns:business.employment_tenure.company M2 .
?x1 ns:business.employer.employees/ns:business.employment_tenure.person M3
}