code: public Observable<GatewayRouteListResultInner> beginGetAdvertisedRoutesAsync(String resourceGroupName, String virtualNetworkGatewayName, String peer) {
          return beginGetAdvertisedRoutesWithServiceResponseAsync(resourceGroupName, virtualNetworkGatewayName, peer).map(new Func1<ServiceResponse<GatewayRouteListResultInner>, GatewayRouteListResultInner>() {
              @Override
              public GatewayRouteListResultInner call(ServiceResponse<GatewayRouteListResultInner> response) {
                  return response.body();
              }
          });
      }
docs: This operation retrieves a list of routes the virtual network gateway is advertising to the specified peer.
  
  @param resourceGroupName The name of the resource group.
  @param virtualNetworkGatewayName The name of the virtual network gateway.
  @param peer The IP address of the peer
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the GatewayRouteListResultInner object