Fix typo

libs/langchain/langchain/retrievers/multi_vector.py

@@ -4,7 +4,7 @@
 from langchain_core.documents import Document
 from langchain_core.pydantic_v1 import Field, validator
 from langchain_core.retrievers import BaseRetriever
-from langchain_core.stores import ByteStore
+from langchain_core.stores import BaseStore, ByteStore
 from langchain_core.vectorstores import VectorStore
 
 from langchain.callbacks.manager import CallbackManagerForRetrieverRun