updated loading in activation patching demo to use transformer bridge

[degenfabian]

Description

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Fixes # (issue)

Type of change

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• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
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Checklist:

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• I have not rewritten tests relating to key interfaces which would affect backward compatibility

[bryce13950]

@degenfabian What's up with the changes made to transformers.py in this PR?

[degenfabian]

@degenfabian What's up with the changes made to transformers.py in this PR?

Cell 8 fails because the devices of the tensors differ (HookedTransformer is on cuda and TransformerBridge is on cpu). I made those changes to mimic how the device selection worked in HookedTransformer (if the user doesn't specify anything, use the best available device on the current machine). This fixed the mismatching output on my laptop, but curiously not in the CI and so far I haven't been able to figure out why.

[bryce13950]

@degenfabian Sounds good! For something like this, that change should be a separate PR, since it may have a benefit in other places