code: static String getIntervalPattern(ChronoPrinter<?> printer) {
  
          AttributeQuery attrs = printer.getAttributes();
  
          if (attrs.contains(Attributes.LANGUAGE)) {
              Locale locale = attrs.get(Attributes.LANGUAGE);
              return CalendarText.patternForInterval(locale);
          }
  
          return "{0}/{1}";
  
      }
docs: <p>Yields the best available format pattern. </p>
  
  @param   printer     chronological component printer
  @return  localized format pattern for intervals
  @since   3.9/4.6