update memory

app.py

@@ -18,6 +18,7 @@ from langchain.utilities import WikipediaAPIWrapper
 from langchain.python import PythonREPL
 from langchain.chains import LLMMathChain
 from langchain.memory import ConversationBufferMemory
+from langchain.memory import ConversationBufferWindowMemory
 from langchain.agents import ZeroShotAgent, AgentExecutor
 from langchain.agents import OpenAIMultiFunctionsAgent
 from langchain.prompts import MessagesPlaceholder
@@ -62,7 +63,7 @@ import langchain
 langchain.debug = True
 memory = ConversationBufferMemory(memory_key="chat_history")
 
-memory_openai = ConversationBufferMemory(memory_key="memory", return_messages=True)
+memory_openai = ConversationBufferWindowMemory(memory_key="memory", return_messages=True)
 
 # Custom document loaders
 class MyElmLoader(UnstructuredEmailLoader):