∀ {α : Type u_1} (P : Array (Array (Array α)) → Prop),
  (∀ (xss : List (List (List α))),
      P (List.map List.toArray (List.map (fun xs => List.map List.toArray xs) xss)).toArray) →
    ∀ (xss : Array (Array (Array α))), P xss