code: public Proxy setProxyAutoconfigUrl(String proxyAutoconfigUrl) {
      verifyProxyTypeCompatibility(ProxyType.PAC);
      this.proxyType = ProxyType.PAC;
      this.proxyAutoconfigUrl = proxyAutoconfigUrl;
      return this;
    }
docs: Specifies the URL to be used for proxy auto-configuration.  Expected format is
  <code>http://hostname.com:1234/pacfile</code>.  This is required if {@link #getProxyType()} is
  set to {@link ProxyType#PAC}, ignored otherwise.
  
  @param proxyAutoconfigUrl the URL for proxy auto-configuration
  @return reference to self