∀ {α : Type u_1} [inst : DecidableEq α] {s : Finset α} (P : Finpartition s),
  P.equivSigmaParts =
    { toFun := fun x => ⟨⟨P.part ↑x, ⋯⟩, ⟨↑x, ⋯⟩⟩, invFun := fun x => ⟨↑x.snd, ⋯⟩, left_inv := ⋯, right_inv := ⋯ }