Get magnetic moment relative to a given spin quantization axis.
        If no axis is provided, moment will be given relative to the
        Magmom's internal spin quantization axis, i.e. equivalent to
        Magmom.moment

        :param axis: (list/numpy array) spin quantization axis
        :return: np.ndarray of length 3

def get_moment(self, saxis=(0, 0, 1)):
        """
        Get magnetic moment relative to a given spin quantization axis.
        If no axis is provided, moment will be given relative to the
        Magmom's internal spin quantization axis, i.e. equivalent to
        Magmom.moment

        :param axis: (list/numpy array) spin quantization axis
        :return: np.ndarray of length 3
        """

        # transform back to moment with spin axis [0, 0, 1]
        m_inv = self._get_transformation_matrix_inv(self.saxis)
        moment = np.matmul(self.moment, m_inv)

        # transform to new saxis
        m = self._get_transformation_matrix(saxis)
        moment = np.matmul(moment, m)

        # round small values to zero
        moment[np.abs(moment) < 1e-8] = 0

        return moment