Update app.py

app.py

@@ -4,6 +4,7 @@ from langchain.chains import ConversationChain
 from langchain.chains.conversation.memory import ConversationBufferWindowMemory
 from langchain.llms import HuggingFacePipeline
 from langchain import PromptTemplate
+from typing import List
 # Load the model and tokenizer
 tokenizer = AutoTokenizer.from_pretrained("gpt2")
 model = AutoModelForCausalLM.from_pretrained("gpt2")