private boolean isFreshnessLifetimeHeuristic(){
  return maxAgeSeconds == -1 && expires == null;
}

private boolean isFreshnessLifetimeHeuristic ( ) { return maxAgeSeconds == - 1 && expires == null ; }
returns true if computefreshnesslifetime used a heuristic . if we used a heuristic to serve a cached response older than 24 hours , we are required to attach a warning .
