code: public Observable<IPAddressAvailabilityResultInner> checkIPAddressAvailabilityAsync(String resourceGroupName, String virtualNetworkName) {
          return checkIPAddressAvailabilityWithServiceResponseAsync(resourceGroupName, virtualNetworkName).map(new Func1<ServiceResponse<IPAddressAvailabilityResultInner>, IPAddressAvailabilityResultInner>() {
              @Override
              public IPAddressAvailabilityResultInner call(ServiceResponse<IPAddressAvailabilityResultInner> response) {
                  return response.body();
              }
          });
      }
docs: Checks whether a private IP address is available for use.
  
  @param resourceGroupName The name of the resource group.
  @param virtualNetworkName The name of the virtual network.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the IPAddressAvailabilityResultInner object