code: @Override
    public boolean visit(final InjectionPlan<?> nodeFrom, final InjectionPlan<?> nodeTo) {
      this.graphStr
          .append("  \"")
          .append(nodeFrom.getClass())
          .append('_')
          .append(nodeFrom.getNode().getName())
          .append("\" -> \"")
          .append(nodeTo.getClass())
          .append('_')
          .append(nodeTo.getNode().getName())
          .append("\" [style=solid];\n");
      return true;
    }
docs: Process current edge of the injection plan.
  
  @param nodeFrom Current injection plan node.
  @param nodeTo   Destination injection plan node.
  @return true to proceed with the next node, false to cancel.