def mrbayes_model_output(Q, eq):
    """
    Output the MrBayes instruction to get user defined rates.

    WARNING: This output is not verified against MrBayes.
    """
    output_string = 'prset aarevmatpr = fixed('
    rate_list = []
    for row in range(1, 20):
        for col in range(0, row):
            r = Q[row, col] / eq[col]
            rate_list.append(f'{r:8.5}')
    output_string += ','.join(rate_list) + ')'
    return output_string
