∀ {𝕜 : Type u_1} {E : Type u_2} [inst : RCLike 𝕜] [inst_1 : SeminormedAddCommGroup E] [inst_2 : InnerProductSpace 𝕜 E]
  {ι : Type u_4} {v : ι → E},
  Orthonormal 𝕜 v →
    ∀ (l₁ l₂ : ι →₀ 𝕜),
      inner 𝕜 ((Finsupp.linearCombination 𝕜 v) l₁) ((Finsupp.linearCombination 𝕜 v) l₂) =
        l₁.sum fun i y => (starRingEnd 𝕜) y * l₂ i