extend 'right' join bug fix (#1718)
extend 'right' join bug fix (#1718)

* extend bug fix

* Update inference_data.py

* Update logic

* Add logic to keep the correct order

* Update logic for add_groups

* Fix long lines
arviz-devs/arviz,arviz-devs/arviz,arviz-devs/arviz,arviz-devs/arviz