public Builder setProxyPreferredAuthSchemes(final Collection<String> proxyPreferredAuthSchemes) {
            this.proxyPreferredAuthSchemes = proxyPreferredAuthSchemes;
            return this;
        }
Determines the order of preference for supported authentication schemes
by their names when authenticating with the proxy host.
<p>
Default: {@code null}
</p>

@return this instance.
httpclient5/src/main/java/org/apache/hc/client5/http/config/RequestConfig.java