A cyclist wearing a black helmet is riding by some black vans.
A person is on a bicycle.
A cyclist is a person.
exists e1 e2 s1 s2 x1 x2 x3 x4.(by(e2,x4) & n_van(x4) & a_black(s2) & Theme(s2,x4) & Actor(e2,x1) & v_ride(e2) & Theme(e1,x3) & Actor(e1,x2) & v_wear(e1) & n_helmet(x3) & a_black(s1) & Theme(s1,x3) & (x1 = x2) & n_cyclist(x1))
exists p1 x1.(exists x2.(on(x1,x2) & n_bicycle(x2)) & n_person(x1))