Add register_module alias to nn.Module (#65174)
Summary:
Fixes https://github.com/pytorch/pytorch/issues/60397. I'm not sure how aliases are supposed to be implemented, but this is the most basic/direct way, IMO. As a side-effect, this implementation results in a "duplicate" doc entry, inheriting the one from `add_module`:
An alternative implementation could be:
```python
def register_module(self, name: str, module: Optional['Module']) -> None:
r"""Alias for :func:`add_module`."""
self.add_module(name, module)
```
which results in this documentation:
Questions:
1. Should I replicate the tests? There are two for `add_module`: [test_add_module_raises_error_if_attr_exists](https://github.com/pytorch/pytorch/blob/873255c6d95342d144e9d1b633c16410844b934e/test/test_nn.py#L1420-L1434) and [test_add_module](https://github.com/pytorch/pytorch/blob/873255c6d95342d144e9d1b633c16410844b934e/test/test_nn.py#L1837-L1855).
2. This PR only adds `register_module` to `nn.Module`. There is an `add_module` in [`_RemoteModule`](https://github.com/pytorch/pytorch/blob/master/torch/distributed/nn/api/remote_module.py#L311-L312), which raises `NotSupported`, and there is another one in [`ConcreteModuleTypeBuilder`](https://github.com/pytorch/pytorch/blob/873255c6d95342d144e9d1b633c16410844b934e/torch/_C/__init__.pyi.in#L468), which means something else, I think. Should I do anything about them?
cc ngimel SsnL
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65174
Reviewed By: soulitzer
Differential Revision: D31089717
Pulled By: jbschlosser
fbshipit-source-id: abd8d14a434fd8c7efa0bd8c242df56da33491e9
