def get_stddevs(self, mean, stddev_types):
        """
        Returns the standard deviations from mean (pg 164; more robust than
        estimate using magnitude)
        """
        mean = np.exp(mean)
        sigma = 0.39 + np.zeros(mean.shape)
        sigma[mean < 0.068] = 0.55
        idx = np.logical_and(mean >= 0.068, mean <= 0.21)
        sigma[idx] = 0.173- 0.140 * np.log(mean[idx])
        stddevs = []
        for stddev in stddev_types:
            if stddev == const.StdDev.TOTAL:
                stddevs.append(sigma)
        return stddevs
Returns the standard deviations from mean (pg 164; more robust than
        estimate using magnitude)