to the core.
*   As every PR requires several CPU/GPU hours of CI testing, we discourage
    submitting PRs to fix one typo, one warning,etc. We recommend fixing the
    same issue at the file level at least (e.g.: fix all typos in a file, fix
    all compiler warnings in a file, etc.)
*   Tests should follow the
    [testing best practices](https://www.tensorflow.org/community/contribute/tests)

    *   Added a short doc explaining how `Estimator`s save checkpoints.
    *   Add documentation for ops supported by the `tf2xla` bridge.
    *   Fix minor typos in the doc of `SpaceToDepth` and `DepthToSpace`.
    *   Updated documentation comments in `mfcc_mel_filterbank.h` and `mfcc.h`
        to clarify that the input domain is squared magnitude spectra and the