Raise warning for unpickable local function (#80140)
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>'
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/80140
Approved by: https://github.com/VitalyFedyunin, https://github.com/NivekT
