}

    @Nonnull
    static ToolchainsBuilderRequestBuilder builder() {
        return new ToolchainsBuilderRequestBuilder();
    }

    @NotThreadSafe
    class ToolchainsBuilderRequestBuilder {
        Session session;
        Source installationToolchainsSource;
        Source userToolchainsSource;

        public ToolchainsBuilderRequestBuilder session(Session session) {
            this.session = session;