∀ (𝕜 : Type u_2) {α : Type u_5} [inst : Zero 𝕜] [inst_1 : One 𝕜] [inst_2 : Preorder α]
  [inst_3 : DecidableRel fun x1 x2 => x1 ⩿ x2] (a b : α), (IncidenceAlgebra.lambda 𝕜) a b = if a ⩿ b then 1 else 0