Function set_item_metadata 

pub fn set_item_metadata<T: Config>(
    collection: CollectionId,
    item: ItemIndex,
    key: MetadataKeyOf<T>,
    value: Option<MetadataValueOf<T>>,
)

Set or remove a metadata default shared by every instance of an item.

This scope overrides the collection default without changing any instance-specific override. Only the collection owner may mutate metadata. None releases an existing entry’s deposit; when the key is absent it is a successful no-op.

Warning: Doc-Only

This function is an automatically generated, and is doc-only, uncallable stub. See the real version in Pallet::set_item_metadata.