Magento – How to get quote item id in checkout_cart_product_add_after observer in magento2

I have setting the custom price of the product on adding to cart which I am doing through some observer .

Everything is working fine except I am not getting the item id in the observer.I tried different ways but not able to get the item id of the added product .

Below is the code for reference. If anybody has some idea please revert.

class CustomPrice implements ObserverInterface
{
    protected $_request;
    protected $_helper;
    protected $cart;
    public function __construct(\Magento\Framework\App\RequestInterface $request,\TW\Product\Helper\Data $helper,\Magento\Checkout\Model\Cart $cart)
    {
        $this->_request = $request;
        $this->_helper = $helper;
        $this->cart=  $cart;
    }

    public function execute(\Magento\Framework\Event\Observer $observer) {

        $writer = new \Zend\Log\Writer\Stream(BP.'/var/log/my.log');
        $logger = new \Zend\Log\Logger();
        $logger->addWriter($writer);

        $reqeustParams = $this->_request->getParams();
        $custom_price = $reqeustParams['custom_price'];

        $item = $observer->getEvent()->getData('quote_item');   


        $item = ( $item->getParentItem() ? $item->getParentItem() : $item );

        $item_id = $item->getId(); **// I get nothing in this**     

        $item->setCustomPrice($custom_price);
        $item->setOriginalCustomPrice($custom_price);
        $item->getProduct()->setIsSuperMode(true);
        $pid = $item->getProductId();
        $logger->info("item id=====pid ".$item_id." ==== ".$pid);
        $this->_helper->updateIteminSession($pid,$item_id);

        //$logger->info("success !!!!");
    }

}

The response which i get on debug is below .. I don't see item id there :

[store_id] => 1
[product (Magento\Catalog\Model\Product\Interceptor)] => Array
    (
        [store_id] => 1
        [row_id] => 1
        [entity_id] => 1
        [created_in] => 1
        [updated_in] => 2147483647
        [attribute_set_id] => 4
        [type_id] => simple
        [sku] => 1
        [has_options] => 0
        [required_options] => 0
        [created_at] => 2017-06-12 08:00:07
        [updated_at] => 2017-06-12 08:00:07
        [name] => Retro Eyeglasses
        [meta_title] => Retro Eyeglasses
        [meta_description] => Retro Eyeglasses 
        [image] => /1/1/118179.jpg
        [small_image] => /1/1/118179.jpg
        [thumbnail] => /1/1/118179.jpg
        [options_container] => container2
        [country_of_manufacture] => US
        [url_key] => retro-eyeglasses
        [gift_message_available] => 2
        [gift_wrapping_available] => 2
        [is_returnable] => 2
        [swatch_image] => /1/1/118179.jpg
        [meta_keyword] => Retro Eyeglasses
        [price] => 12.9500
        [weight] => 1.0000
        [status] => 1
        [visibility] => 4
        [quantity_and_stock_status] => Array
            (
                [is_in_stock] => 1
                [qty] => 999997
            )

        [tax_class_id] => 2
        [options] => Array
            (
            )

        [media_gallery] => Array
            (
                [images] => Array
                    (
                        [1] => Array
                            (
                                [value_id] => 1
                                [file] => /1/1/118179.jpg
                                [media_type] => image
                                [row_id] => 1
                                [position] => 1
                                [disabled] => 0
                                [position_default] => 1
                                [disabled_default] => 0
                            )

                    )

                [values] => Array
                    (
                    )

            )

        [category_ids] => Array
            (
                [0] => 3
            )

        [tier_price] => Array
            (
            )

        [tier_price_changed] => 0
        [is_salable] => 1
        [website_ids] => Array
            (
                [0] => 1
            )

        [cart_qty] => 1
        [qty] => 1
        [event] => 
    )

[product_id] => 1
[product_type] => simple
[sku] => 1
[name] => Retro Eyeglasses
[weight] => 1.0000
[tax_class_id] => 2
[is_qty_decimal] => 
[qty_to_add] => 1
[qty] => 1
[qty_options] => Array
    (
    )