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# next(isolation:)

Produces the next element in the map sequence.

```
mutating func next(isolation actor: isolated (any Actor)?) async throws(AsyncMapSequence<Base, Transformed>.Failure) -> Transformed?
```

## Discussion

This iterator calls `next(isolation:)` on its base iterator; if this
call returns `nil`, `next(isolation:)` returns `nil`. Otherwise,
`next(isolation:)` returns the result of calling the transforming
closure on the received element.

---

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