proposition: Theorem isfibseqg {Y Z : UU} (g : Y -> Z) (z : Z) : isfibseq (hfiberpr1 g z) g z (λ ye: _, pr2 ye).
proof: Proof. intros. simple refine (isweqhomot _ _ _ (idisweq _)). - intro. apply idpath. Defined.
imports: UniMath.Foundations.Preamble