gtin13 constant
gtin13 [Expects: https://schema.org/Text]
The GTIN-13 code of the product, or the product to which the offer refers. This is equivalent to 13-digit ISBN codes and EAN UCC-13. Former 12-digit UPC codes can be converted into a GTIN-13 code by simply adding a preceding zero. See GS1 GTIN Summary for more details.
Can be used on: https://schema.org/Demand, https://schema.org/Offer, https://schema.org/Product
Implementation
static const gtin13 = IriTerm.prevalidated('https://schema.org/gtin13');