code: public Chronology getChronology(Object object, Chronology chrono) {
          if (chrono == null) {
              chrono = ((ReadablePartial) object).getChronology();
              chrono = DateTimeUtils.getChronology(chrono);
          }
          return chrono;
      }
docs: Gets the chronology, which is taken from the ReadableInstant.
  <p>
  If the passed in chronology is non-null, it is used.
  Otherwise the chronology from the instant is used.
  
  @param object  the ReadablePartial to convert, must not be null
  @param chrono  the chronology to use, null means use that from object
  @return the chronology, never null