SwiftDocCUtility APIsAPI CollectionUtility APIsTopicsErrorsprotocol DescribedErrorAn error that offers a plain-text error message.Languagestruct EnglishLanguageFunctions providing tools for generating English language.struct NativeLanguageA structure allowing for adding further languages in the future.URLsstruct ValidatedURLAn RFC 3986 compliant URL.Auxiliarystruct ChecksumA checksum generator.struct FeatureFlagsA set of feature flags that conditionally enable (usually experimental) behavior in Swift-DocC.