*   boosted trees: adding pruning mode.
    *   tf.train.Checkpoint does not delete old checkpoints by default.
    *   tfdbg: Limit the total disk space occupied by dumped tensor data to 100
        GBytes. Add environment variable `TFDBG_DISK_BYTES_LIMIT` to allow
        adjustment of this upper limit.

## Thanks to our Contributors

designed to prevent `:hover` stickiness on iOS-an issue where hover styles\n// would persist after initial touch.\n//\n// For backward compatibility, we've kept these mixins and updated them to\n// always return their regular pseudo-classes instead of a shimmed media query.\n//\n// Issue: https://github.com/twbs/bootstrap/issues/25195\n\n@mixin hover() {\n  &:hover { @content; }\n}\n\n@mixin hover-focus() {\n  &:hover,\n  &:focus {\n    @content;\n  }\n}\n\n@mixin plain-hover-focus() {\n  &,\n  &:hover,\n...