def get_lomb_amplitude_ratio(lomb_model, i):
    """
    Get the ratio of the amplitudes of the first harmonic for the ith and first
    frequencies from a fitted Lomb-Scargle model.
    """
    return lomb_model['freq_fits'][i - 1]['amplitude'][0] / lomb_model[
        'freq_fits'][0]['amplitude'][0]
