unfold vset.index
ρ : Config F
t : TraceRel'
d : Delta'
⊢ vset.index {a | (a ∈ t ∧ (a.1.1, a.2) ∈ d.add ∨ a ∈ t ∧ (a.1.1, a.2) ∈ d.delete) ∨ a ∈ t ∧ (a.1.1, a.2) ∈ d.modify}
      ρ =
    restrict (vset.index t ρ) (indexDelta d ρ)
ρ : Config F
t : TraceRel'
d : Delta'
⊢ (fun x =>
      {a | (a ∈ t ∧ (a.1.1, a.2) ∈ d.add ∨ a ∈ t ∧ (a.1.1, a.2) ∈ d.delete) ∨ a ∈ t ∧ (a.1.1, a.2) ∈ d.modify} (x, ρ)) =
    restrict (fun x => t (x, ρ)) (indexDelta d ρ)