**Please** add a meaningful description for your change here

------------------------

Follow this checklist to help us incorporate your contribution quickly and easily:

 - [ ] Format the pull request title like `[BEAM-XXX] Fixes bug in ApproximateQuantiles`, where you replace `BEAM-XXX` with the appropriate JIRA issue, if applicable. This will automatically link the pull request to the issue.
 - [ ] If this contribution is large, please file an Apache [Individual Contributor License Agreement](https://www.apache.org/licenses/icla.pdf).

It will help us expedite review of your Pull Request if you tag someone (e.g. `@username`) to look at it.
