clear method

Implementation

void clear() {
  if (value is Map) {
    if ((value as Map).containsKey('selected-start') &&
        (value as Map).containsKey('selected-end')) {
      (value as Map)['selected-start'] = null;
      (value as Map)['selected-end'] = null;
    } else {
      (value as Map)['selected'] = null;
    }
  } else {
    value = null;
  }
}