Constant ENTITY_ITEMS 

pub const ENTITY_ITEMS: EntityCapabilityKey<dyn ResourceHandler<ItemResource>>;

An entity’s items, as NeoForge 26.3’s Capabilities.Item.ENTITY. The game answers it for a player with their inventory (PlayerInventoryWrapper): indices as vanilla’s Inventory numbers them, 0..36 the main inventory (0..9 the hotbar), 36..40 the armour from feet to head, 40 the off hand. For a chest or hopper minecart, a chest boat, or a chested donkey, mule or llama, it answers with their container’s slots (ItemPlace::EntitySlot).