public Optional<String> getProxyDomain() {
        return Optional.ofNullable(proxyDomain);
    }
Returns the optional Windows domain name for configuring an NTLM proxy. If you aren't using a
Windows NTLM proxy, you do not need to set this field.

@return The optional Windows domain name for configuring an NTLM proxy.
aws-java-sdk-opensdk/src/main/java/com/amazonaws/opensdk/config/ProxyConfiguration.java