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# init(healthStore:device:start:)

Creates a new heartbeat series builder.

```
init(healthStore: HKHealthStore, device: HKDevice?, start startDate: Date)
```

## Parameters

`healthStore`

The HealthKit store.

`device`

An object representing the device that provided the heartbeat data. Pass `nil` if the app is generating its own data.

`startDate`

The sample’s start date.

---

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