when 'SEG_POLY_WRITE_CONVERSION'
        usage = "SEG_POLY_WRITE_CONVERSION <Lower Bound> <C0> <C1> <C2> ..."
        parser.verify_num_parameters(2, nil, usage)
        if !(@current_item.write_conversion &&
             SegmentedPolynomialConversion === @current_item.write_conversion)