    # File lib/rvg/rvg.rb, line 163
            def background_position=(pos)
                warn "background_position= has no effect in nested RVG objects" if @nested
                bg_pos = pos.to_s.downcase
                if ! ['scaled', 'tiled', 'fit'].include?(bg_pos)
                    raise ArgumentError, "background position must be `scaled', `tiled', or `fit' (#{pos} given)"
                end
                @background_position = bg_pos.to_sym
            end