How can we associate simple product to bundle product programmatically in Magento 2

Question

I have added bundle product programmatically by using below code but how can i associate a simple product to bundle product programmatically.

    /** @var $objectManager \Magento\TestFramework\ObjectManager */
$objectManager = \Magento\Framework\App\ObjectManager::getInstance(); // instance of object manager
$state = $objectManager->get('Magento\Framework\App\State');
//$state->setAreaCode('frontend');
$_product = $objectManager->create('Magento\Catalog\Model\Product');
$_product->setCategoryIds(array(3,5));
$_product->setName('Test Product6');
$_product->setTypeId('bundle');
$_product->setAttributeSetId(4);
$_product->setSku('test-SKU6');
$_product->setAttributeSetId(11);
$_product->setWebsiteIds(array(1));
$_product->setVisibility(4);
$_product->setPrice(array(1));
$_product->setImage('/testimg/test.jpg');
$_product->setSmallImage('/testimg/test.jpg');
$_product->setThumbnail('/testimg/test.jpg');
$_product->setStatus(\Magento\Catalog\Model\Product\Attribute\Source\Status::STATUS_ENABLED);
$_product->setStockData(array(
        'use_config_manage_stock' => 0, //'Use config settings' checkbox
        'manage_stock' => 1, //manage stock
        'min_sale_qty' => 1, //Minimum Qty Allowed in Shopping Cart
        'max_sale_qty' => 2, //Maximum Qty Allowed in Shopping Cart
        'is_in_stock' => 1, //Stock Availability
        'qty' => 100 //qty
        )
    );

$_product->save();

I have tried this answer but i am getting error

Help would be appreciated.