The Lean 4 theorem `coe_sum_single` in the `ChapterNavierStokesIkebeKato` chapter of the timepiece formalization

-- Generated from ChapterNavierStokesIkebeKato.lean — theorem BookProof.NavierStokesFlow.IkebeKato.coe_sum_single
import Mathlib
import Definitions.Def_ChapterNavierStokesIkebeKato
import Definitions.Def_ChapterNavierStokesAffineFiberEsa
open BookProof.NavierStokesFlow
open BookProof.NavierStokesFlow.IkebeKato


open scoped ENNReal



open LpNat BookProof.FarisLavine

variable {ι : Type*}

theorem BookProof.NavierStokesFlow.IkebeKato.coe_sum_single [DecidableEq ι] (S : Finset ι) (u : ι → ℂ) (k : ι) :
    ((∑ i ∈ S, lp.single 2 i (u i) : L2I ι) : ι → ℂ) k = if k ∈ S then u k else 0 := by sorry