def METHOD_NAME(q, tol=ATOL):
    """Checks if a quaternion is unit-length.
    Parameters
    ----------
    q : [float, float, float, float] | :class:`~compas.geometry.Quaternion`
        Quaternion or sequence of four floats ``[w, x, y, z]``.
    tol : float, optional
        Requested decimal precision.
    Returns
    -------
    bool
        True if the quaternion is unit-length,
        and False if otherwise.
    """
    n = quaternion_norm(q)
    return allclose([n], [1.0], tol)