def subscribe_to_shell_stream(
        self, callback: Callable[[str], None] | None = None
    ) -> bool:
        """
        Subscribe to shell command output stream.
        This method is meant to be overridden by runtime implementations
        that want to stream shell command output to external consumers.

        Args:
            callback: A function that will be called with each line of output from shell commands.
                     If None, any existing subscription will be removed.

        Returns False by default.
        """
        return False

        Subscribe to shell command output stream.
        This method is meant to be overridden by runtime implementations
        that want to stream shell command output to external consumers.

        Args:
            callback: A function that will be called with each line of output from shell commands.
                     If None, any existing subscription will be removed.

        Returns False by default.
        
openhands/runtime/base.py