⊦ ns = ns0 ↔ (∀ n. n ∈ ns ↔ n ∈ ns0)
∀ ns0. # ns0 < # ns → true → ns0.keys.inodes? ⊦ # ns = 0, ns.keys.inodes?, ∀ n. n ∈ ns ↔ n ∈ ∅
Used terms: ∅, ns