Woocommerce upsell with checkboxes

/**
 * Add upsells as extra data for added product
 */
function add_upsells_to_cart( $cart_item_key ) {
    global $woocommerce;

    if ( empty( $_REQUEST['upsells'] ) || ! is_array( $_REQUEST['upsells'] ) )
        return;

    // Prevent loop
    $upsells = $_REQUEST['upsells'];
    unset( $_REQUEST['upsells'] );

    // Append each upsells to product in cart
    foreach( $upsells as $upsell_id ) {
        $upsell_id = absint( $upsell_id );

        // Add upsell into cart and set upsell_of as extra key with parent product item id
        $woocommerce->cart->add_to_cart( $upsell_id, 1, '', '', array( 'upsell_of' => $cart_item_key ) );
    }
}
add_action( 'woocommerce_add_to_cart', 'add_upsells_to_cart', 1, 6 );


/**
 * Inject upsell_of extra key cart item key when cart is loaded from session
 */
function get_cart_items_from_session( $item, $values, $key ) {
    if ( array_key_exists( 'upsell_of', $values ) )
        $item[ 'upsell_of' ] = $values['upsell_of'];

    return $item;
}
add_filter( 'woocommerce_get_cart_item_from_session', 'get_cart_items_from_session', 1, 3 );


/**
 * Remove associated upsells if product removed from cart
 */
function remove_upsells_from_cart( $cart_item_key ) {
    global $woocommerce;

    // Get cart
    $cart = $woocommerce->cart->get_cart();

    // For each item in cart, if item is upsell of deleted product, delete it
    foreach( $cart as $upsell_key => $upsell )
        if ( $upsell['upsell_of'] == $cart_item_key )
            unset( $woocommerce->cart->cart_contents[ $upsell_key ] );
}
add_action( 'woocommerce_before_cart_item_quantity_zero', 'remove_upsells_from_cart' );

<?php wp_reset_query(); ?>

get_post_meta( $item['product_id'], '_crosssell_ids', true )

foreach ( $items as $item ) {
$product_crosssell_ids = get_post_meta( $item['product_id'], '_crosssell_ids', true );

if (is_array($product_crosssell_ids) && !empty($product_crosssell_ids)){
$cross_ids = array_unique( array_merge( $product_crosssell_ids, $cross_ids )) ;
}

}