Remove return value for __exit__ (#32997)
Summary:
When an error is raised and `__exit__` in a context manager returns `True`, the error is suppressed; otherwise the error is raised. No return value should be given to maintain the default behavior of context manager.
Fixes https://github.com/pytorch/pytorch/issues/32639. The `get_lr` function was overridden with a function taking an epoch parameter, which is not allowed. However, the relevant error was not being raised.
```python
In [1]: import torch
...:
...: class MultiStepLR(torch.optim.lr_scheduler._LRScheduler):
...: def __init__(self, optimizer, gamma, milestones, last_epoch = -1):
...: self.init_lr = [group['lr'] for group in optimizer.param_groups]
...: self.gamma = gamma
...: self.milestones = milestones
...: super().__init__(optimizer, last_epoch)
...:
...: def get_lr(self, step):
...: global_step = self.last_epoch #iteration number in pytorch
...: gamma_power = ([0] + [i + 1 for i, m in enumerate(self.milestones) if global_step >= m])[-1]
...: return [init_lr * (self.gamma ** gamma_power) for init_lr in self.init_lr]
...:
...: optimizer = torch.optim.SGD([torch.rand(1)], lr = 1)
...: scheduler = MultiStepLR(optimizer, gamma = 1, milestones = [10, 20])
```
```
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
<ipython-input-1-7fad6ba050b0> in <module>
14
15 optimizer = torch.optim.SGD([torch.rand(1)], lr = 1)
---> 16 scheduler = MultiStepLR(optimizer, gamma = 1, milestones = [10, 20])
<ipython-input-1-7fad6ba050b0> in __init__(self, optimizer, gamma, milestones, last_epoch)
6 self.gamma = gamma
7 self.milestones = milestones
----> 8 super().__init__(optimizer, last_epoch)
9
10 def get_lr(self, step):
~/anaconda3/envs/pytorch/lib/python3.7/site-packages/torch/optim/lr_scheduler.py in __init__(self, optimizer, last_epoch)
75 self._step_count = 0
76
---> 77 self.step()
78
79 def state_dict(self):
~/anaconda3/envs/pytorch/lib/python3.7/site-packages/torch/optim/lr_scheduler.py in step(self, epoch)
141 print("1a")
142 # try:
--> 143 values = self.get_lr()
144 # except TypeError:
145 # raise RuntimeError
TypeError: get_lr() missing 1 required positional argument: 'step'
```
May be related to https://github.com/pytorch/pytorch/issues/32898.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/32997
Differential Revision: D19737731
Pulled By: vincentqb
fbshipit-source-id: 5cf84beada69b91f91e36b20c3278e9920343655
