GTIN product xml

Hello. I use Product GTIN (EAN, UPC, ISBN) for WooCommerce and i want to add the field to the xml. How do i use the meta or the shortcode to add the field to the xml feed? Th.e meta is _wpm_gtin_code. And the info of the shortcode is:

The shortcode to show the GTIN code is [wpm_product_gtin] you can use these attributes:

id the product id
label the label that will be displayed before the code. By default is “Code EAN:”, but this can be changed inside the settings panel.
wrapper you can wrap the label and GTIN code in div or span. By default is ‘div’ for the shop page and ‘span’ on the other pages.
wrapper_code the container of GTIN code. By default is a ‘span’.
class the class of wrapper container. By default is ‘wpm_gtin’.
class_wrapper the class of wrapper code container. By default is ‘wpm_gtin_code_wrapper’.

Thanks in advanced.

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