Update document_chat.py

document_chat.py

@@ -4,7 +4,7 @@ from langchain.embeddings import HuggingFaceEmbeddings
 from langchain.document_loaders import PyMuPDFLoader
 from langchain.text_splitter import RecursiveCharacterTextSplitter
 from langchain.chains import ConversationalRetrievalChain
-from langchain.memory import ConversationalBufferMemory
+from langchain.memory import ConversationBufferMemory
 from langchain.llms import HuggingFaceHub
 
 #Constants