fix moved imports for langchain 0.5

fiscal.py

@@ -6,14 +6,22 @@ from langchain_community.vectorstores import Chroma
 from langchain_community.retrievers import BM25Retriever
 from langchain_core.prompts import PromptTemplate
 from langchain_core.documents import Document
-from langchain.chains import ConversationalRetrievalChain
-from langchain.memory import ConversationBufferMemory
 
 try:
     from langchain.retrievers import EnsembleRetriever
 except ImportError:
     from langchain_community.retrievers import EnsembleRetriever
 
+try:
+    from langchain.chains import ConversationalRetrievalChain
+except ImportError:
+    from langchain_community.chains import ConversationalRetrievalChain
+
+try:
+    from langchain.memory import ConversationBufferMemory
+except ImportError:
+    from langchain_community.memory import ConversationBufferMemory
+
 # ---------- Embeddings ----------
 embeddings = HuggingFaceEmbeddings(
     model_name="nomic-ai/nomic-embed-text-v1",