Disable Shipping from Documentation not Working

I followed the documentation to disable shipping, but it isnt working as expected, is there a free plugin that could disable shipping for a crowdfunding product, i added this code below in line 55 on wpcrowdfunding/includes/woocommerce/woocommerce.php and keep getting errors:

add_filter( 'woocommerce_cart_needs_shipping_address', array($this, 'disable_shipping') );
add_filter( 'woocommerce_cart_ready_to_calc_shipping', array($this, 'disable_shipping'), 99);
function disable_shipping() {
    global $woocommerce;
    $has_crowdfunding_product = false;
    $items = $woocommerce->cart->get_cart();
    if( $items) {
        foreach($items as $item => $values) {
            $product = wc_get_product( $values['product_id'] );
            if( $product->get_type() == 'crowdfunding' ){
                $has_crowdfunding_product = true;
            }
        }
    }
    return !$has_crowdfunding_product;
}