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# HealthKit Constants

## Topics

### Constants

[`HKDataTypeIdentifierStateOfMind`](/documentation/HealthKit/HKDataTypeIdentifierStateOfMind)

[`HKMetadataKeyAppleFitnessPlusCatalogIdentifier`](/documentation/HealthKit/HKMetadataKeyAppleFitnessPlusCatalogIdentifier)

[`HKMetadataKeyMaximumLightIntensity`](/documentation/HealthKit/HKMetadataKeyMaximumLightIntensity)

A key that indicates the maximum intensity of light for an outdoor time sample.

[`HKPredicateKeyPathWorkoutEffortRelationship`](/documentation/HealthKit/HKPredicateKeyPathWorkoutEffortRelationship)


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