@Override
    public WebClientBuilder decorator(
            Function<? super HttpClient, ? extends HttpClient> decorator) {
        return (WebClientBuilder) super.decorator(decorator);
    }
Returns a newly-created web client based on the properties of this builder.

@throws IllegalArgumentException if the scheme of the {@code uri} specified in
                                 {@link WebClient#builder(String)} or
                                 {@link WebClient#builder(URI)} is not an HTTP scheme
core/src/main/java/com/linecorp/armeria/client/WebClientBuilder.java