∀ {I₁ : Type u_1} {I₂ : Type u_2} {I₁₂ : Type u_4} {c₁ : ComplexShape I₁} {c₂ : ComplexShape I₂}
  {c₁₂ : ComplexShape I₁₂} {inst : TotalComplexShape c₁ c₂ c₁₂} {inst_1 : TotalComplexShape c₂ c₁ c₁₂}
  [self : TotalComplexShapeSymmetry c₁ c₂ c₁₂] (i₁ : I₁) {i₂ i₂' : I₂},
  c₂.Rel i₂ i₂' →
    TotalComplexShapeSymmetry.σ c₁ c₂ c₁₂ i₁ i₂ * c₁.ε₂ c₂ c₁₂ (i₁, i₂) =
      c₂.ε₁ c₁ c₁₂ (i₂, i₁) * TotalComplexShapeSymmetry.σ c₁ c₂ c₁₂ i₁ i₂'