item method

Implementation

@override
String item(int index) {
  if (index < _properties.length) {
    return _properties.keys.elementAt(index);
  }
  int remaining = index - _properties.length;
  for (final String key in _pendingProperties.keys) {
    if (_properties.containsKey(key)) continue;
    if (remaining == 0) return key;
    remaining--;
  }
  throw RangeError.index(index, this, 'index', null, length);
}