* Split out changes from #3563 to make that PR easier to review. This formats the file according to the Black formatter
* Store a reference to the trainer on the datamodule
Fixes#3682
* Update data_connector.py
* Update data_connector.py
* Update test_datamodules.py
* Split out changes from #3563 to make that PR easier to review. This formats the file according to the Black formatter
* support checkpoint hooks for datamodule
refactor on_{save/load}_checkpoint to a separate hook class that both the lightning module and data module inherit
add spots in callback connector to call new datamodule hooks if available
* hooks formatting
* Update hooks.py
* Update checkpoint_connector.py
* Update lightning.py
* update based on upstream/master
checkout upstream/master
* Update checkpoint_connector.py
* add tests
* undo format revert
* Updated CHANGELOG.md
* add checkpoint hooks
* add Dict type
* import CheckpointHooks