added Hybrid Search with BM25

app.py

@@ -327,8 +327,9 @@ class BSIChatbot:
             allDocs = self.retrieveDocFromFaiss()
             bm25_retriever = BM25Retriever.from_documents(allDocs)
             #TODO!
-            bm25_retriever.k= 4
-            vectordb = vectorstore.as_retriever(search_kwargs={"k":4})
+            retriever_k=15
+            bm25_retriever.k= retriever_k
+            vectordb = vectorstore.as_retriever(search_kwargs={"k":retriever_k})
             ensemble_retriever = EnsembleRetriever(retrievers=[bm25_retriever, vectordb], weights=[0.5, 0.5])
             retrieved_chunks = ensemble_retriever.get_relevant_documents(query)
             print("DBG: Number of Chunks retrieved")