public class ExampleModDataGenerator implements DataGeneratorEntrypoint {

    // ... (The rest of the file)

    private static class MyTagGenerator extends FabricTagProvider.ItemTagProvider {

        // ... (The rest of the file)

        private static final TagKey<Item> SMELLY_ITEMS = TagKey.of(RegistryKeys.ITEM, new Identifier("mymod:smelly_items"));

        @Override
        protected void configure(WrapperLookup arg) {
          // This creates a tag builder, where we add slime balls, rotten flesh and everything in the minecraft:dirt item tag.
          // This will automatically generate "src/main/generated/data/tutorial/tags/items/smelly_items.json" in the "generated" folder.
          getOrCreateTagBuilder(SMELLY_ITEMS)
                  .add(Items.SLIME_BALL)
                  .add(Items.ROTTEN_FLESH)
                  .addOptionalTag(ItemTags.DIRT);
        }
    }
}