test.py

#%%
from operator import itemgetter

from langchain.chat_models import ChatOpenAI
from langchain.memory import ConversationBufferMemory
from langchain.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_core.runnables import RunnableLambda, RunnablePassthrough

model = ChatOpenAI()
prompt = ChatPromptTemplate.from_messages(
    [
        ("system", "You are a helpful chatbot"),
        MessagesPlaceholder(variable_name="history"),
        ("human", "{input}"),
    ]
)
memory = ConversationBufferMemory(return_messages=True)

memory.load_memory_variables({})
#%%
chain = (
    RunnablePassthrough.assign(
        history=RunnableLambda(memory.load_memory_variables) | itemgetter("history")
    )
    | prompt
    | model
)

inputs = {"input": "hi im bob"}
response = chain.invoke(inputs)
response
#%%
memory.save_context(inputs, {"output": response.content})