code: public ServiceFuture<VpnSiteInner> beginCreateOrUpdateAsync(String resourceGroupName, String vpnSiteName, VpnSiteInner vpnSiteParameters, final ServiceCallback<VpnSiteInner> serviceCallback) {
          return ServiceFuture.fromResponse(beginCreateOrUpdateWithServiceResponseAsync(resourceGroupName, vpnSiteName, vpnSiteParameters), serviceCallback);
      }
docs: Creates a VpnSite resource if it doesn't exist else updates the existing VpnSite.
  
  @param resourceGroupName The resource group name of the VpnSite.
  @param vpnSiteName The name of the VpnSite being created or updated.
  @param vpnSiteParameters Parameters supplied to create or update VpnSite.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object