factory YoutubeResponse.fromJSON(Map YoutubeResponseJson) 
 {

// Below 2 line code is parsing JSON Array of items in our JSON Object (YouttubeResponse)


var list = YoutubeResponseJson['items'] as List;
List itemsList = list.map((i) => Item.fromJSON(i)).toList();

return new YoutubeResponse(
    kind: YoutubeResponseJson['kind'],
    etag: YoutubeResponseJson['etag'],
    nextPageToken: YoutubeResponseJson['nextPageToken'],
    regionCode: YoutubeResponseJson['regionCode'],
    mPageInfo: pageInfo.fromJSON(YoutubeResponseJson['pageInfo']),

    // Here we are returning parsed JSON Array.

    items: itemsList);

  }