langchain/document_loaders/slack_directory.py/SlackDirectoryLoader/_get_message_source
class SlackDirectoryLoader:    def _get_message_source(self, channel_name: str, user: str, timestamp: str) -> str:
        """
        Get the message source as a string.

        Args:
            channel_name (str): The name of the channel the message belongs to.
            user (str): The user ID who sent the message.
            timestamp (str): The timestamp of the message.

        Returns:
            str: The message source.
        """
        if self.workspace_url:
            channel_id = self.channel_id_map.get(channel_name, "")
            return (
                f"{self.workspace_url}/archives/{channel_id}"
                + f"/p{timestamp.replace('.', '')}"
            )
        else:
            return f"{channel_name} - {user} - {timestamp}"