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# NSCollectionViewDiffableDataSource.SupplementaryViewProvider

A closure that configures and returns a collection view’s supplementary view, such as a header or footer, from a diffable data source.

```
typealias SupplementaryViewProvider = (NSCollectionView, String, IndexPath) -> (any NSView & NSCollectionViewElement)?
```

## Parameters

`collectionView`

The collection view to configure this supplementary view for.

`kind`

The kind of supplementary view to provide. The layout object that supports the supplementary view defines the value of this string.

`indexPath`

The index path that specifies the location of the supplementary view in the collection view.

## Return Value

A non-`nil` configured supplementary view object. The supplementary view provider must return a valid view object to the collection view.

---

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