def bondi_constraints(self, lhs=True, rhs=True):
    """Compute Bondi-gauge constraint equations

    Bondi gauge establishes some relations that the data must satisfy:

        ψ̇₀ = ðψ₁ + 3 σ ψ₂
        ψ̇₁ = ðψ₂ + 2 σ ψ₃
        ψ̇₂ = ðψ₃ + 1 σ ψ₄
        ψ₃ = -∂ðσ̄/∂u
        ψ₄ = -∂²σ̄/∂u²
        Im[ψ₂] = -Im[ð²σ̄ + σ ∂σ̄/∂u]

    This function returns a 6-tuple of 2-tuples, corresponding to these 6 equations
    and their left- and right-hand sides.

    """
    return (
        self.bianchi_0(lhs, rhs),
        self.bianchi_1(lhs, rhs),
        self.bianchi_2(lhs, rhs),
        self.constraint_3(lhs, rhs),
        self.constraint_4(lhs, rhs),
        self.constraint_mass_aspect(lhs, rhs),
    )