code: public ServiceFuture<List<VirtualMachineScaleSetExtensionInner>> listAsync(final String resourceGroupName, final String vmScaleSetName, final ListOperationCallback<VirtualMachineScaleSetExtensionInner> serviceCallback) {
          return AzureServiceFuture.fromPageResponse(
              listSinglePageAsync(resourceGroupName, vmScaleSetName),
              new Func1<String, Observable<ServiceResponse<Page<VirtualMachineScaleSetExtensionInner>>>>() {
                  @Override
                  public Observable<ServiceResponse<Page<VirtualMachineScaleSetExtensionInner>>> call(String nextPageLink) {
                      return listNextSinglePageAsync(nextPageLink);
                  }
              },
              serviceCallback);
      }
docs: Gets a list of all extensions in a VM scale set.
  
  @param resourceGroupName The name of the resource group.
  @param vmScaleSetName The name of the VM scale set containing the extension.
  @param serviceCallback the async ServiceCallback to handle successful and failed responses.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the {@link ServiceFuture} object