[BUG] Pytorch module hooks are not executed

[abhaybd]

Describe the bug
I'm trying to debug some issues during online training (using fit_online) using pytorch hooks, but these hooks are not being executed. Looking at the code, policies are explicitly calling self.forward() like this. Directly calling self.forward() doesn't execute any hooks (see this post), so __call__() should be used instead. So self.forward() should be replaced with self().

To Reproduce

1. Register a hook with the policy module, e.g. algo._impl.policy.register_module_forward_pre_hook(hook)
2. Train with algo.fit_online(...)
3. Observe that the hook is never invoked

Expected behavior
The registered hooks should be executed.

Additional context
N/A.

[takuseno]

Thanks for the issue. This issue has been resolved in the latest master branch.