    # File lib/rvg/embellishable.rb, line 103
                def round(rx, ry=nil)
                    rx, ry = Magick::RVG.convert_to_float(rx, ry || rx)
                    if rx < 0 || ry < 0
                        raise ArgumentError, "rx, ry must be >= 0 (#{rx}, #{ry} given)"
                    end
                    @args << rx << ry
                    @primitive = :roundrectangle
                    self
                end