calculate_right_margin (SVG::Graph::Graph)

    # File temp/Graph/Graph.rb, line 391
          def calculate_right_margin
            @border_right = 7
            if key and key_position == :right
              val = keys.max { |a,b| a.length <=> b.length }
              @border_right += val.length * key_font_size * 0.6
              @border_right += KEY_BOX_SIZE
              @border_right += 10    # Some padding around the box
            end
          end