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## Description
<!-- Provide a clear description of the changes in this PR -->
- Expose top_k as an optional argument of run_question_answering
- Update retrievers to handle the parameters
## DCO Affirmation
I affirm that all code in every commit of this pull request conforms to
the terms of the Topoteretes Developer Certificate of Origin
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## Summary by CodeRabbit
- **New Features**
- Enhanced answer generation and document retrieval capabilities by
introducing an optional parameter that allows users to specify the
number of top results. This improvement adds flexibility when retrieving
question responses and associated context, adapting the output based on
user preference.
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