Refactor retriever.py to initialize SentenceSplitter and update BM25Retriever instantiation

retriever.py

@@ -1,6 +1,7 @@
 from llama_index.core.schema import Document
 from llama_index.core.tools import FunctionTool
 from llama_index.retrievers.bm25 import BM25Retriever
+from llama_index.core.node_parser import SentenceSplitter
 
 import datasets
 
@@ -22,7 +23,13 @@ docs = [
     for guest in guest_dataset
 ]
 
-bm25_retriever = BM25Retriever.from_documents(docs)
+
+
+
+# initialize node parser
+splitter = SentenceSplitter(chunk_size=512)
+nodes = splitter.get_nodes_from_documents(docs)
+bm25_retriever = BM25Retriever.from_defaults(nodes=nodes) 
 
 def get_guest_info_retreiver(query: str) -> str:
     """Fetches guest information based on the query."""