Update app.py

app.py

@@ -8,7 +8,7 @@ from langchain_community.embeddings import HuggingFaceEmbeddings
 from langchain_community.vectorstores import Chroma
 from langchain_community.document_loaders import UnstructuredPDFLoader
 from langchain.text_splitter import CharacterTextSplitter
-from langchain.chains.qa_with_sources import RetrievalQAWithSourcesChain
+from langchain.chains import RetrievalQAWithSourcesChain  # Modifica qui
 from langchain.schema import Document
 from langchain.memory import ConversationBufferMemory
 from langchain.callbacks.manager import CallbackManager