SwiftDocCAvailabilityIndexClassAvailabilityIndexThe AvailabilityIndex class stores the information about availability for SDKs of symbols. The information if a symbol is available for a given platform and version is stored inside this index.class AvailabilityIndexTopicsStructuresstruct InfoA single entry in the index.Initializersinit()init(from: any Decoder) throwsInstance Propertiesvar interfaceLanguages: Set<InterfaceLanguage>The set containing all the interface languages in the index.var platforms: Set<Platform.Name>Instance Methodsfunc add(language: InterfaceLanguage)Insert a language inside the index.func add(platform: Platform.Name, for: InterfaceLanguage)Insert a language inside the index.func encode(to: any Encoder) throwsfunc id(for: AvailabilityIndex.Info, createIfMissing: Bool) -> Int?func info(for: Int) -> AvailabilityIndex.Info?func platform(for: Platform.Name.ID) -> Platform.Name?Returns a Platform for a given ID.func platform(named: String) -> Platform.NameReturns a Platform.Name with a given String, otherwise return the undefined platform.func platforms(for: InterfaceLanguage) -> [Platform.Name]?Returns a list of platforms for a given language.func sortedVersions(for: Platform.Name) -> [Platform.Version]?Returns an array containing the versions for a given platform in ascending order.func versions(for: Platform.Name) -> Set<Platform.Version>?Returns a set containing the versions for a given platform.