📚 The doc issue

In current docstring of forward_hook, it says:

What's the meaning of It can modify the input inplace but it will not have effect on forward while The hook can modify the output. also holds?

When I check the implementation of Module, the result of forward is indeed overridden by hook_result as long as the hook function returns a modified result.

Suggest a potential alternative/fix

I suppose the above docstring to be modified as follows:

     The hook can modify the module output as long as it returns 
     the modified output. It cannot modify the given argument `output` 
     inplace since this is called after :func:`forward` is called. 

cc @brianjo @mruberry @albanD @jbschlosser @walterddr @kshitij12345