no goals
α : Type u
β : α → Type v
inst✝ : DecidableEq α
s₁ s₂ s₃ : AList β
⊢ ∀ (x : α) (y : β x), y ∈ dlookup x (s₁ ∪ s₂ ∪ s₃).entries ↔ y ∈ dlookup x (s₁ ∪ (s₂ ∪ s₃)).entries
simp [not_or, or_assoc, and_or_left, and_assoc]