def METHOD_NAME(self, now: rospy.Time | None = None):
    """
    Deletes expired objects. Should be called frequently to clear expired objects.
    Args:
        now (rospy.Time): The time to compare to each object's timestamp to see
            if it has expired and needs to be removed from :attr:`.objects`.
    """
    if now is None:
        now = rospy.Time.now()
    self.objects = list(
        filter(lambda obj: now - obj.stamp < self.expiration_seconds, self.objects),
    )