Example to add meta data to woocommerce cart items

gistfile1.php

<?php

/*
 * Plugin Name:  Example Modify Price
 */
class Example_Modify_Price {
  private static $instance;

	public static function register() {
		if (self::$instance == null) {
			self::$instance = new Example_Modify_Price();
		}
	}

	public function __construct() {
		// Add to cart
		add_filter('woocommerce_add_cart_item', array($this, 'add_cart_item'), 10, 1);

		// Add item data to the cart
		add_filter('woocommerce_add_cart_item_data', array($this, 'add_cart_item_data'), 10, 2);

		// Load cart data per page load
		add_filter('woocommerce_get_cart_item_from_session', array($this, 'get_cart_item_from_session'), 10, 2);

		// Validate when adding to cart
		add_filter('woocommerce_add_to_cart_validation', array($this, 'validate_add_cart_item'), 10, 3);


		// Add meta to order
		add_action('woocommerce_order_item_meta', array($this, 'order_item_meta'), 10, 2);

		// Add meta to order - WC 2.x
		add_action('woocommerce_add_order_item_meta', array($this, 'order_item_meta_2'), 10, 2);
	}

	/**
	 * add_cart_item function.
	 *
	 * @access public
	 * @param mixed $cart_item
	 * @return void
	 */
	function add_cart_item($cart_item) {

		$extra_cost = 10.00;
		$cart_item['data']->adjust_price($extra_cost);

		return $cart_item;
	}

	/**
	 * get_cart_item_from_session function.
	 *
	 * @access public
	 * @param mixed $cart_item
	 * @param mixed $values
	 * @return void
	 */
	function get_cart_item_from_session($cart_item, $values) {
		$cart_item = $this->add_cart_item($cart_item);
		return $cart_item;
	}

	/**
	 * order_item_meta function.
	 *
	 * @access public
	 * @param mixed $item_meta
	 * @param mixed $cart_item
	 * @return void
	 */
	function order_item_meta($item_meta, $cart_item) {
		$item_meta->add('Your Meta Name', 'Your Meta Value');
	}

	/**
	 * order_item_meta_2 function.
	 *
	 * @access public
	 * @param mixed $item_id
	 * @param mixed $values
	 * @return void
	 */
	function order_item_meta_2($item_id, $values) {
		if (function_exists('woocommerce_add_order_item_meta')) {

			woocommerce_add_order_item_meta($item_id, 'Your Meta Name', 'Your Meta Value');
		}
	}

}

Example_Modify_Price::register();

Where's the function add_cart_item_data() refereed in add_filter('woocommerce_add_cart_item_data', array($this, 'add_cart_item_data'), 10, 2);