code: public Observable<Page<BuildTaskInner>> listAsync(final String resourceGroupName, final String registryName, final String filter, final String skipToken) {
          return listWithServiceResponseAsync(resourceGroupName, registryName, filter, skipToken)
              .map(new Func1<ServiceResponse<Page<BuildTaskInner>>, Page<BuildTaskInner>>() {
                  @Override
                  public Page<BuildTaskInner> call(ServiceResponse<Page<BuildTaskInner>> response) {
                      return response.body();
                  }
              });
      }
docs: Lists all the build tasks for a specified container registry.
  
  @param resourceGroupName The name of the resource group to which the container registry belongs.
  @param registryName The name of the container registry.
  @param filter The build task filter to apply on the operation.
  @param skipToken $skipToken is supported on get list of build tasks, which provides the next page in the list of tasks.
  @throws IllegalArgumentException thrown if parameters fail the validation
  @return the observable to the PagedList&lt;BuildTaskInner&gt; object