Return basis vector lengths

    Parameters
    ----------
    lattice : array_like
        Basis vectors given as column vectors
        shape=(3, 3), dtype='double'

    Returns
    -------
    ndarray, shape=(3,), dtype='double'

def _get_lattice_parameters(lattice):
    """Return basis vector lengths

    Parameters
    ----------
    lattice : array_like
        Basis vectors given as column vectors
        shape=(3, 3), dtype='double'

    Returns
    -------
    ndarray, shape=(3,), dtype='double'

    """

    return np.array(np.sqrt(np.dot(lattice.T, lattice).diagonal()),
                    dtype='double')