    # File lib/rvg/rvg.rb, line 141
            def background_image=(bg_image)
                warn "background_image= has no effect in nested RVG objects" if @nested
                if bg_image && ! bg_image.kind_of?(Magick::Image)
                    raise ArgumentError, "background image must be an Image (got #{bg_image.class})"
                end
                @background_image = bg_image
            end