Adding memory

This shows how to add memory to an arbitrary chain. Right now, you can use the memory classes but need to hook it up manually

from operator import itemgetter
from langchain.chat_models import ChatOpenAI
from langchain.memory import ConversationBufferMemory
from langchain.schema.runnable import RunnablePassthrough, RunnableLambda
from langchain.prompts import ChatPromptTemplate, MessagesPlaceholder

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({})

    {'history': []}

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

inputs = {"input": "hi im bob"}
response = chain.invoke(inputs)
response

    AIMessage(content='Hello Bob! How can I assist you today?', additional_kwargs={}, example=False)

memory.save_context(inputs, {"output": response.content})

memory.load_memory_variables({})

    {'history': [HumanMessage(content='hi im bob', additional_kwargs={}, example=False),
      AIMessage(content='Hello Bob! How can I assist you today?', additional_kwargs={}, example=False)]}

inputs = {"input": "whats my name"}
response = chain.invoke(inputs)
response

    AIMessage(content='Your name is Bob.', additional_kwargs={}, example=False)