def _convert_dvcrel1(dvcrel, xyz_scale):
    """helper for ``_convert_optimization``"""
    element_type = dvcrel.element_type
    if element_type == 'CBUSH':
        if dvcrel.cp_name in ['X1', 'X2', 'X3', 'S', 'S1', 'S2', 'S3']:
            scale = xyz_scale
        else:
            raise NotImplementedError(dvcrel)
    else:
        raise NotImplementedError(dvcrel)
    return scale
