# 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