apiSpec: ApiSpec
): Sequence<KotlinExtensionFunction> =

    api.allTypes()
        .filter { type -> type.isPublic && apiSpec.isApi(type.sourceName) }
        .flatMap { type -> kotlinExtensionFunctionsFor(type, sinceSupplier) }
        .distinctBy(::signatureKey)


private
fun signatureKey(extension: KotlinExtensionFunction): List<Any> = extension.run {
    listOf(targetType.sourceName, name) +