langchain/memory/chat_message_histories/zep.py/ZepChatMessageHistory/__init__
class ZepChatMessageHistory:    def __init__(
        self,
        session_id: str,
        url: str = "http://localhost:8000",
    ) -> None:
        try:
            from zep_python import ZepClient
        except ImportError:
            raise ValueError(
                "Could not import zep-python package. "
                "Please install it with `pip install zep-python`."
            )

        self.zep_client = ZepClient(base_url=url)
        self.session_id = session_id