Let X, S and F be given.
Assume HF Hnon.
We will prove intersection_of_family X F basis_of_subbasis X S.
An exact proof term for the current goal is (SepI (finite_intersections_of X S) (λb : setb Empty) (intersection_of_family X F) (ReplI (finite_subcollections S) (λF0 : setintersection_of_family X F0) F HF) Hnon).