Fix pickling of KFoldLoop (#12441)

* allow pickling of KFoldLoop

* Update pl_examples/loop_examples/kfold.py

Co-authored-by: Adrian Wälchli <aedu.waelchli@gmail.com>
Co-authored-by: Nicolas Berger <nicolas.berger@inait.ai>
Co-authored-by: Kushashwa Ravi Shrimali <kushashwaravishrimali@gmail.com>

CHANGELOG.md

@@ -16,6 +16,8 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed an issue wrt recursive invocation of DDP configuration in hpu parallel plugin ([#12912](https://github.com/PyTorchLightning/pytorch-lightning/pull/12912))
 - Fixed printing of ragged dictionaries in `Trainer.validate` and `Trainer.test` ([#12857](https://github.com/PyTorchLightning/pytorch-lightning/pull/12857))
 - Fixed threading support for legacy loading of checkpoints ([#12814](https://github.com/PyTorchLightning/pytorch-lightning/pull/12814))
+- Fixed pickling of `KFoldLoop` ([#12441](https://github.com/PyTorchLightning/pytorch-lightning/pull/12441))
+- Stopped `optimizer_zero_grad` from being called after IPU execution ([#12913](https://github.com/PyTorchLightning/pytorch-lightning/pull/12913))
 
 
 ## [1.6.2] - 2022-04-27

pl_examples/loop_examples/kfold.py

@@ -239,6 +239,9 @@ class KFoldLoop(Loop):
             return getattr(self.fit_loop, key)
         return self.__dict__[key]
 
+    def __setstate__(self, state: Dict[str, Any]) -> None:
+        self.__dict__.update(state)
+
 
 class LitImageClassifier(ImageClassifier):
     def __init__(self) -> None: