Woocommerce pre-orders plugin allow multiple products in cart

woocommerce-pre-orders-plugin-allow-multiple-products-in-cart.php

<?php

//remove pre-order limitations --> only one item per order
function ax_remove_validation_cart(){
	if (!empty($GLOBALS['wc_pre_orders'])){
	  remove_filter( 'woocommerce_add_to_cart_validation', array( $GLOBALS['wc_pre_orders']->cart, 'validate_cart' ), 15, 2 );	
	}
}
add_action( 'init', 'ax_remove_validation_cart' );