Reschedule this call for a later time

        @type secondsLater: C{float}
        @param secondsLater: The number of seconds after the originally
        scheduled time for which to reschedule this call.

        @raise AlreadyCancelled: Raised if this call has been cancelled.
        @raise AlreadyCalled: Raised if this call has already been made.

def delay(self, secondsLater):
        """Reschedule this call for a later time

        @type secondsLater: C{float}
        @param secondsLater: The number of seconds after the originally
        scheduled time for which to reschedule this call.

        @raise AlreadyCancelled: Raised if this call has been cancelled.
        @raise AlreadyCalled: Raised if this call has already been made.
        """
        if self.cancelled:
            raise error.AlreadyCancelled
        elif self.called:
            raise error.AlreadyCalled
        else:
            self.delayed_time += secondsLater
            if self.delayed_time < 0:
                self.activate_delay()
                self.resetter(self)