def delay(
            self,
            identifier: typing.Any,
            until: typing.Union[int, float]=-1,
    ) -> bool:
        """Delay a deferred function until the given time.

        Args:
            identifier (typing.Any): The identifier returned from a call
                to defer or defer_for.
            until (typing.Union[int, float]): A numeric value that represents
                the clock time when the callback becomes available for
                execution. Values that are less than the current time result in
                the function being called at the next opportunity.

        Returns:
            bool: True if the call is delayed. False if the identifier is
                invalid or if the deferred call is already executed.
        """
        raise NotImplementedError()