code: public boolean isSupported(DurationFieldType type) {
          if (type == null) {
              return false;
          }
          return type.getField(getChronology()).isSupported();
      }
docs: Checks if the duration type specified is supported by this
  local datetime and chronology.
  
  @param type  a duration type, usually obtained from DurationFieldType
  @return true if the field type is supported