Proofgold Proof

pf
Let x0 of type ι be given. Let x1 of type ι be given. Assume H0: x1 ∈ x0. Let x2 of type ι → ο be given. Assume H1: ∀ x3 x4 . x4 ∈ x3 ⟶ x2 (pack_e x3 x4). Apply H1 with x0, x1. The subproof is completed by applying H0. ■