code: @Override
      public IRenderingElement generate(IReaction reaction, RendererModel model) {
          Rectangle2D totalBoundsReactants = BoundsCalculator.calculateBounds(reaction.getReactants());
          Rectangle2D totalBoundsProducts = BoundsCalculator.calculateBounds(reaction.getProducts());
  
          if (totalBoundsReactants == null || totalBoundsProducts == null) return null;
  
          double separation = model.getParameter(BondLength.class).getValue()
                  / model.getParameter(Scale.class).getValue();
          Color foregroundColor = model.getParameter(BasicSceneGenerator.ForegroundColor.class).getValue();
          return new ArrowElement(totalBoundsReactants.getMaxX() + separation, totalBoundsReactants.getCenterY(),
                  totalBoundsProducts.getMinX() - separation, totalBoundsReactants.getCenterY(), 1 / model.getParameter(
                          Scale.class).getValue(), true, foregroundColor);
      }
docs: {@inheritDoc}