proposition: Lemma foqc_axioms r f: equivalence r -> function f -> source f = substrate r -> f \coP (section_canon_proj r).
proof: Proof. move=> er ff sf. split =>//; first by apply: section_canon_proj_f. by rewrite /section_canon_proj; aw. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)