code: function castProductIDsToNumbers( cartItems ) {
  	return cartItems.map( function( item ) {
  		return assign( {}, item, { product_id: parseInt( item.product_id, 10 ) } );
  	} );
  }
docs: FIXME: Temporary fix to cast string product IDs to numbers. There is a bug with the API where it sometimes returns product IDs as strings.