Fix find_tied_params for models with shared layers

[qubvel]

What does this PR do?

Fixes #2984

Before submitting

• This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
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• Did you write any new necessary tests?

Who can review?

@SunMarc

[HuggingFaceDocBuilderDev]

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[qubvel]

Added a test case that fails

FAILED tests/test_modeling_utils.py::ModelingUtilsTester::test_find_tied_parameters - AssertionError: assert [] == [['0.weight',...s', '1.bias']]
  
  Right contains 2 more items, first extra item: ['0.weight', '1.weight']
  
  Full diff:
  + []
  - [
  -     [
  -         '0.weight',
  -         '1.weight',
  -     ],
  -     [
  -         '0.bias',
  -         '1.bias',
  -     ],
  - ]

[qubvel]

CI error looks unrelated:

Cannot access gated repo for url https://huggingface.co/meta-llama/Llama-2-7b-hf/resolve/main/config.json.
Access to model meta-llama/Llama-2-7b-hf is restricted. You must be authenticated to access it.
======== 1 failed, 29 passed, 1 skipped, 1 warning in 65.21s (0:01:05) =========
make: *** [Makefile:34: test_cli] Error 1

@SunMarc, its ready for review

[SunMarc]

Thanks for fixing the issue @qubvel ! LGTM ! Just a nit !

[SunMarc]

Can you have a second look @muellerzr ?

[muellerzr]

Thanks! I like this simplicity and thanks for adding the test. A few suggestions for clarity

[muellerzr]

If we're documenting it in this way, we should make this public :)

[qubvel]

not sure you need it public :) its just copied form PyTorch code

[qubvel]

I removed Example for this docstring, not sure it is needed for a private method, and also doc-builder was raising an error (commit #952324c)

[qubvel]

@SunMarc I suppose it can be merged!

[muellerzr]

Yes indeed, thanks @qubvel !