Was M2 edited by a person , edited by M0 's editor , and edited by M3
SELECT count(*) WHERE {
?x0 ns:film.editor.film M0 .
?x1 a ns:people.person .
M2 ns:film.film.edited_by ?x0 .
M2 ns:film.film.edited_by ?x1 .
M2 ns:film.film.edited_by M3
}