refactor(hf): merge an override into the section's own dict, with no fallback

A section read from either config type has its dict in the data being merged:
PretrainedConfig.to_dict serializes every sub-config the config holds, and
RawConfigShim wraps only the dicts it holds. The `or {}` fallback was reached
only by a section a config class computes in a property, as transformers'
PeAudioVideoConfig does, and there the whole-section write it produced was
refused at the re-init ("property ... has no setter"); such an override now
fails at the merge, naming the section. _with_overrides takes the two config
types it is handed.

Author: YevheniiKotyrlo

python/freetoken/utils/hf.py

@@ -234,12 +234,12 @@ def _load_hf_config(model_path: str) -> Any:
     return config
 
 
-def _with_overrides(config: Any, data: dict, overrides: Mapping[str, Any]) -> dict:
+def _with_overrides(config: PretrainedConfig | RawConfigShim, data: dict, overrides: Mapping[str, Any]) -> dict:
     merged = dict(data)
     for key, value in overrides.items():
         section = getattr(config, key, None)
         if isinstance(value, Mapping) and isinstance(section, (PretrainedConfig, RawConfigShim)):
-            merged[key] = _with_overrides(section, merged.get(key) or {}, value)
+            merged[key] = _with_overrides(section, merged[key], value)
         else:
             merged[key] = copy.deepcopy(value)
     return merged