public function append(NodeDefinition $node)
    {
        if ($node instanceof ParentNodeDefinitionInterface) {
            $builder = clone $this;
            $builder->setParent(null);
            $node->setBuilder($builder);
        }

        if (null !== $this->parent) {
            $this->parent->append($node);
            // Make this builder the node parent to allow for a fluid interface
            $node->setParent($this);
        }

        return $this;
    }