def __convert_frequency_dict_to_rates(freq_dict):
    """ Converts a Frequency Dictionary to a Probability Dictionary

    :param dict freq_dict: Dictionary of Frequencies of Occurrence

    :return: Dictionary of Probabilities/Rates of Occurrence
    :rtype: dict

    """
    n_tot = sum(freq_dict.values())
    for k in freq_dict.keys():
        freq_dict[k] /= n_tot

    return freq_dict