code: public void beginDownload(String resourceGroupName, String virtualWANName, GetVpnSitesConfigurationRequest request) {
          beginDownloadWithServiceResponseAsync(resourceGroupName, virtualWANName, request).toBlocking().single().body();
      }
docs: Gives the sas-url to download the configurations for vpn-sites in a resource group.
  
  @param resourceGroupName The resource group name.
  @param virtualWANName The name of the VirtualWAN for which configuration of all vpn-sites is needed.
  @param request Parameters supplied to download vpn-sites configuration.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @throws ErrorException thrown if the request is rejected by server
  @throws RuntimeException all other wrapped checked exceptions if the request fails to be sent