gtin12 constant
gtin12 [Expects: https://schema.org/Text]
The GTIN-12 code of the product, or the product to which the offer refers. The GTIN-12 is the 12-digit GS1 Identification Key composed of a U.P.C. Company Prefix, Item Reference, and Check Digit used to identify trade items. 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 gtin12 = IriTerm.prevalidated('https://schema.org/gtin12');