def shift(self, delay: float) -> None:
        """Advance timeout on delay seconds.

        The delay can be negative.

        Raise RuntimeError if shift is called when deadline is not scheduled
        """
        deadline = self._deadline
        if deadline is None:
            raise RuntimeError("cannot shift timeout if deadline is not scheduled")
        self.update(deadline + delay)
Advance timeout on delay seconds.

        The delay can be negative.

        Raise RuntimeError if shift is called when deadline is not scheduled
        
lib/async_timeout/__init__.py