∀ {𝕜 : Type u_2} {α : Type u_5} [inst : AddCommGroup 𝕜] [inst_1 : One 𝕜] [inst_2 : PartialOrder α]
  [inst_3 : LocallyFiniteOrder α] [inst_4 : DecidableEq α] (a b : α),
  ∑ x ∈ Finset.Icc a b, (IncidenceAlgebra.mu'✝ 𝕜) x b = if a = b then 1 else 0