I need to display the **block** in product detail page for bundle product only
so I just add preference to overwrite **Magento/Catalog/Controller/Product/View**

Then alter the product detail page controller execute method like below.

	// Render page
	$page = $this->resultPageFactory->create();
	            
	if($this->_type->getById($productId)->getTypeId()=='bundle')
	{
	    $block=$page->getLayout()->createBlock('Training3\BundleBlock\Block\Index\Index');
	    $page->getLayout()->getBlock('content')->append($block);
	}      

	$this->viewHelper->prepareAndRender($page, $productId, $this, $params);
	return $page;

but it always throws error like 

>PHP Fatal error:  Call to a member function append() on boolean

I need to add my block to `<referenceContainer name="content">`