Refactor the utilities file into utilities folder

[starship006]

Description

Addresses #612

As of this comment being written, this only currently just refactors utils - no extra testing has been added.

Type of change

Please delete options that are not relevant.

• 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)
• This change requires a documentation update

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

[starship006]

Okay, currently slightly confused about something. There is weird behavior around USE_DEFAULT_VALUE = None in the utilities. In some parts of the code this is being treated as an optional boolean, and other parts its an optional string.

Right now, we are facing
transformer_lens/utilities/exploratory_utils.py:23: error: Cannot determine type of "USE_DEFAULT_VALUE" [has-type]

But, whenever I add the type USE_DEFAULT_VALUE: Optional[bool] = None to it, it causes typing checks downstream to fail, such as:

transformer_lens/HookedTransformer.py:293: error: Argument 3 to "get_attention_mask" has incompatible type "bool | None"; expected "bool"  [arg-type]
transformer_lens/HookedTransformer.py:366: error: Incompatible default for argument "padding_side" (default has type "bool | None", argument has type "Literal['left', 'right'] | None")

@bryce13950 , what is the best way to proceed? is there something obvious here I'm missing?

[bryce13950]

Sorry for not getting back to you earlier. Honestly, I think the whole USE_DEFAULT_VALUE is not adding value to the code, and it is mostly overcomplicating the readability. if prepend_bos is None: is a lot more readable than if prepend_bos is USE_DEFAULT_VALUE:. If you come across something like = USE_DEFAULT_VALUE, then I would just replace it with USE_DEFAULT_VALUE = None. I would like to remove it and replace it with None for all type hinting, but that is a bit beyond the scope of this task. We can pretty safely do it for booleans though.