code: public int decide(final LoggingEvent event) {
      boolean accepted = true;
      Filter f = headFilter;
      while (f != null) {
        accepted = accepted && (Filter.ACCEPT == f.decide(event));
        f = f.next;
      }
      if (accepted) {
        if(acceptOnMatch) {
          return Filter.ACCEPT;
        }
         return Filter.DENY;
      }
      return Filter.NEUTRAL;
    }
docs: If this event does not already contain location information,
  evaluate the event against the expression.
  
  If the expression evaluates to true, generate a LocationInfo instance
  by creating an exception and set this LocationInfo on the event.
  
  Returns {@link Filter#NEUTRAL}