code: public Observable<Page<P2SVpnGatewayInner>> listByResourceGroupAsync(final String resourceGroupName) {
          return listByResourceGroupWithServiceResponseAsync(resourceGroupName)
              .map(new Func1<ServiceResponse<Page<P2SVpnGatewayInner>>, Page<P2SVpnGatewayInner>>() {
                  @Override
                  public Page<P2SVpnGatewayInner> call(ServiceResponse<Page<P2SVpnGatewayInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Lists all the P2SVpnGateways in a resource group.
  
  @param resourceGroupName The resource group name of the P2SVpnGateway.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;P2SVpnGatewayInner&gt; object