def _SNR(coef):
    """
    Return the signal-to-noise ratio for each constituent.
    """
    if "Lsmaj" in coef:
        SNR = (coef["Lsmaj"] ** 2 + coef["Lsmin"] ** 2) / (
            (coef["Lsmaj_ci"] / 1.96) ** 2 + (coef["Lsmin_ci"] / 1.96) ** 2
        )
    else:
        SNR = (coef["A"] ** 2) / (coef["A_ci"] / 1.96) ** 2
    return SNR