A gio.proxy_resolver.ProxyResolver to use with this session.
If no proxy resolver is set, then the default proxy resolver will be used. See gio.proxy_resolver.ProxyResolver.getDefault. You can set it to null if you don't want to use proxies, or set it to your own gio.proxy_resolver.ProxyResolver if you want to control what proxies get used.
Builder instance for fluent chaining
Set proxyResolver property.