WatchOS detect if body present for heart rate

Question

In watchOS, is there a way to detect if a body is present to determine whether or not to show a heart rate?

I am finding that when I take the watch off, the heart rate sensor keeps returning values. I want to show "-" when the watch is taken off.

Below is the function I am using to get the heart rate.

Thanks.

private func heartRateQuery(quantityTypeIdentifier: HKQuantityTypeIdentifier) {
    
    // We want data points from our current device
    let devicePredicate = HKQuery.predicateForObjects(from: [HKDevice.local()])
    
    // A query that returns changes to the HealthKit store, including a snapshot of new changes and continuous monitoring as a long-running query.
    let updateHandler: (HKAnchoredObjectQuery, [HKSample]?, [HKDeletedObject]?, HKQueryAnchor?, Error?) -> Void = {
        query, samples, deletedObjects, queryAnchor, error in
        
        // A sample that represents a quantity, including the value and the units.
        guard let samples = samples as? [HKQuantitySample] else {
            return
        }
        
        self.process(samples, type: quantityTypeIdentifier)
        
    }
    
    // Provides with both the ability to receive a snapshot of data, and then on subsequent calls, a snapshot of what has changed.
    let query = HKAnchoredObjectQuery(type: HKObjectType.quantityType(forIdentifier: quantityTypeIdentifier)!, predicate: devicePredicate, anchor: nil, limit: HKObjectQueryNoLimit, resultsHandler: updateHandler)

    
    query.updateHandler = updateHandler
    
    // query execution
    healthStore.execute(query)
}

private func processHeartRate(_ samples: [HKQuantitySample], type: HKQuantityTypeIdentifier) {
           
    // Variable initialization
    var lastHeartRate = 0.0
    
    // Get the first sample value
    guard let sample = samples.first else{
        print("No samples!")
        return
    }
    
    // Get current heart rate        
    if type == .heartRate {
        lastHeartRate = sample.quantity.doubleValue(for: heartRateQuantity)
        
        self.value = Int(lastHeartRate)
        hrLabel.setText(String(value))
        print("The lastHeartRate is  \(lastHeartRate)")            
    }

}