# callAsFunction(_:eventHandler:) Performs the transformation on an input sequence. ``` func callAsFunction(_ input: S, eventHandler: EventHandler? = nil) async throws -> Self.OutputSequence where S : TemporalSequence, Self.Input == S.Feature ``` ## Parameters `input` The input temporal sequence. `eventHandler` An event handler. ## Return Value An async sequence produced by applying the transformation to the input. --- Copyright © 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)