WooCommerce カート内の商品価格をプログラムで変更するにはどうすればよいですか?

// Set custom cart item price
add_action( 'woocommerce_before_calculate_totals', 'add_custom_price', 1000, 1);

// Handle mini cart custom item price (Optional)
if ( ! is_admin() || defined( 'DOING_AJAX' ) ) :
    add_filter( 'woocommerce_cart_item_price', 'filter_cart_item_price', 10, 3 );
endif;

// Respective Functions
function add_custom_price( $cart ) {
   // Required for WC 3.0+
   if ( is_admin() && ! defined( 'DOING_AJAX' ) )
       return;

   // Avoid hook repetition
   if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
       return;

   // Loop through cart items
   foreach ( $cart->get_cart() as $cart_item ) {
       $cart_item['data']->set_price( 40 );
   }
}

function filter_cart_item_price( $price_html, $cart_item, $cart_item_key ) {
   if ( isset( $cart_item['custom_price'] ) ) {
       $args = array( 'price' => 40 );

       if ( WC()->cart->display_prices_including_tax() ) {
           $product_price = wc_get_price_including_tax( $cart_item['data'], $args );
       } else {
           $product_price = wc_get_price_excluding_tax( $cart_item['data'], $args );
       }
       return wc_price( $product_price );
   }
   return $price_html;
}