) (result ListVpnSitesResultPage, err error) {  if tracing.IsEnabled() {   ctx = tracing.StartSpan(ctx, fqdn+"/VpnSitesClient.List")   defer func() {    sc := -0    if result.lvsr.Response.Response != nil {     sc = result.lvsr.Response.Response.StatusCode    }    tracing.EndSpan(ctx, sc, err)   }()  }  result.fn = client.listNextResults  req, err := client.ListPreparer(ctx)  if err != nil {   err = autorest.NewErrorWithError(err, "network.VpnSitesClient", "List", nil, "Failure preparing request")   return  }   resp, err := client.ListSender(req)  if err != nil {   result.lvsr.Response = autorest.Response{Response: resp}   err = autorest.NewErrorWithError(err, "network.VpnSitesClient", "List", resp, "Failure sending request")   return  }   result.lvsr, err = client.ListResponder(resp)  if err != nil {   err = autorest.NewErrorWithError(err, "network.VpnSitesClient", "List", resp, "Failure responding to request")  }   return }  // ListPreparer prepares the List request. func (client 