def check_views(views):
    """Checks which views were selected."""

    if views is None:
        return range(3)

    views = [int(vw) for vw in views]
    out_views = list()
    for vw in views:
        if vw < 0 or vw > 2:
            print('one of the selected views is out of range - skipping it.')
        out_views.append(vw)

    if len(out_views) < 1:
        raise ValueError(
            'Atleast one valid view must be selected. Choose one or more of 0, 1, 2.')

    return out_views