def check_thickness(s):
    """
    Check and parse thickness specs as either a single [s] or a list of [s,s,s,...]
    """

    s = check_1d(s, "thickness")
    if any(map(lambda d: d <= 0, s)):
        raise Exception('Thickness cannot be 0 or negative')

    return s
Check and parse thickness specs as either a single [s] or a list of [s,s,s,...]