Fix type annotation in RetrieverWithSource class

lawchatbot/retrievers.py

@@ -1,6 +1,7 @@
 from langchain_core.retrievers import BaseRetriever
 from langchain.retrievers.bm25 import BM25Retriever
 from langchain_core.documents import Document
+from typing import Any
 from langchain.retrievers import EnsembleRetriever
 
 def initialize_semantic_retriever(vectorstore, config) -> BaseRetriever:
@@ -63,7 +64,7 @@ def wrap_retriever_with_source(retriever):
     Wraps a retriever so every returned document has a 'source' key in metadata.
     """
     class RetrieverWithSource(BaseRetriever):
-        base_retriever: any
+        base_retriever: Any
 
         def __init__(self, base_retriever):
             super().__init__()