Raise warning for unpickable local function (#547) (#80232)
Summary:
X-link: https://github.com/pytorch/data/pull/547
Fixes https://github.com/pytorch/data/issues/538
- Improve the validation function to raise warning about unpickable function when either lambda or local function is provided to DataPipe.
- The inner function from functools.partial object is extracted as well for validation
- Mimic the behavior of pickle module for local lambda function: It would only raise Error for the local function rather than lambda function. So, we will raise warning about local function not lambda function.
```py
>>> import pickle
>>> def fn():
... lf = lambda x: x
... pickle.dumps(lf)
>>> pickle.dumps(fn)
AttributeError: Can't pickle local object 'fn.<locals>.<lambda>'
```
This Diff also fixes the Error introduced by https://github.com/pytorch/pytorch/pull/79344
Test Plan:
CI on PyTorch and TorchData
Manually validated the tests from TorchVision
Differential Revision: D37417556
Pull Request resolved: https://github.com/pytorch/pytorch/pull/80232
Approved by: https://github.com/NivekT
