and
    [GPU developer Dockerfile](https://github.com/tensorflow/tensorflow/blob/master/tensorflow/tools/dockerfiles/dockerfiles/devel-gpu.Dockerfile)
    for the required packages. Alternatively, use the said
    [tensorflow/build Docker images](https://hub.docker.com/r/tensorflow/build)
    (`tensorflow/tensorflow:devel` and `tensorflow/tensorflow:devel-gpu` are no
    longer supported for) development. Use TF SIG Build Dockerfiles in

## Bug Fixes and Other Changes

*   `tf.image`
    *   Added an optional parameter `return_index_map` to `tf.image.ssim` which
        causes the returned value to be the local SSIM map instead of the global
        mean.

*   TF Core:

    *   `tf.custom_gradient` can now be applied to functions that accept