Six pyright errors followed the same pattern: a value flowed out of
`self._settings.X` (typed `T | _NotGiven`) into a context that wanted
the plain `T`. Wrap each with `assert_given(...)` so the sentinel
gets stripped at the boundary:
- aws/nova_sonic/llm.py: `_settings.model` (in InvokeModel...Input)
and `_settings.system_instruction` (passed to the adapter).
- deepgram/flux/base.py: iterating `_settings.keyterm`.
- google/stt.py: iterating `_settings.languages`.
- google/tts.py: iterating `_settings.speaker_configs`.
- openai/base_llm.py: `_settings.system_instruction` passed to the
adapter.
Also takes a deeper pass at the related Google STT issue: the override
of `language_to_service_language` had been broadened to take
`Language | list[Language]` and return `str | list[str]`, a Liskov
violation against the base's `Language -> str | None` contract.
External callers always pass a single Language, and the only consumer
of the list path was Google STT's own `_get_language_codes`. Restore
the override to a single-Language signature and let
`_get_language_codes` iterate. The override is also tightened to
return `str` (narrower than the base's `str | None`, which is
LSP-compatible) since it always falls back to `"en-US"` rather than
returning None.
Net: -7 pyright errors (full-config run: 782 -> 775).
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