code: @Nonnull
    public CacheControlBuilder setSharedMaxAgeSeconds (@Nonnegative final long nSeconds)
    {
      ValueEnforcer.isGE0 (nSeconds, "Seconds");
      m_aSharedMaxAgeSeconds = Long.valueOf (nSeconds);
      return this;
    }
docs: Set the maximum age for shared caches in seconds relative to the request
  time. Similar to max-age, except that it only applies to shared (e.g.,
  proxy) caches.
  
  @param nSeconds
  Seconds to keep it
  @return this