[Bug Report] `TransformerBridge.boot_*` methods are invisible to static type checkers

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
76/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
python
Domain
developer-experience, tooling

Research direction

Read transformer_lens/model_bridge.py and the three source locations named in the report: sources/transformers/__init__.py:31, sources/native/__init__.py:115, and sources/tl_legacy.py:226. Compare the boot_* signatures and decide how to expose them to static type checkers while preserving the bridge-to-sources import direction. Done when calls such as TransformerBridge.boot_native(cfg) are recognized and have a typed return value.

Written by the indexing model from the issue text.

Description

boot_transformers, boot_native and boot_tl_legacy are attached to TransformerBridge at import time with setattr(TransformerBridge, "boot_...", staticmethod(boot)), in sources/transformers/__init__.py:31, sources/native/__init__.py:115 and sources/tl_legacy.py:226. Because the class body never declares them, static type checkers flag every call, even though the package ships py.typed:

from transformer_lens.model_bridge import TransformerBridge
model = TransformerBridge.boot_native(cfg)
# ty: Class `TransformerBridge` has no attribute `boot_native`

It also means no autocomplete and an untyped return value in editors.

Workaround: from transformer_lens.model_bridge.sources import boot_native. This works and is fully typed.

Possible fixes, which keep the bridge → sources import direction intact:

  • Declare the methods on the class under if TYPE_CHECKING:, using the source signatures, or
  • Define them as real @staticmethods on TransformerBridge that lazily import and delegate to the source boot.

Versions: transformer-lens 4.3.0, ty 0.0.97, Python 3.14

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