[Python] How do I update my get_history() function to use...

I’m updating a LangChain-based app to use the new langchain_postgres package instead of the deprecated langchain_community.chat_message_histories.

Previously, my function looked like this:

from langchain_community.chat_message_histories import PostgresChatMessageHistory
import os

def get_history(session_id: str) -> PostgresChatMessageHistory:
connection_string = os.getenv("POSTGRES_CONNECTION_STRING")
if not connection_string:
raise ValueError("POSTGRES_CONNECTION_STRING environment variable is not set")

return PostgresChatMessageHistory(
session_id=session_id,
connection_string=connection_string,
table_name="chat_message_history",
)


After switching from:

from langchain_community.chat_message_histories import PostgresChatMessageHistory

to:

from langchain_postgres import PostgresChatMessageHistory

…I get this warning in VSCode:

Expected 2 more positional arguments (Pylance reportCallIssue)

What I’ve Tried

I understand that the new PostgresChatMessageHistory requires more arguments, but I can’t find updated documentation or examples that clarify which ones are mandatory and what values to use for them.

Question

What is the correct way to rewrite my get_history() function to work with langchain_postgres.PostgresChatMessageHistory?

Thanks in advance!

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