import folder into After Effects CC by using ExtendScript

Hi, I am trying to import folder by using Adobe Extendscript into AE CC2018. The function should be same as AE import folder function. Please see attachment below.

Attachment below is result in AE after  "Import Folder" button is pressed.

I try to using Extendscript importFile() methods to import folder, but  no luck. 

app.project.importFile(new ImportOptions(new Folder("C:\\Users\\Username\\Desktop\\type\\line")));

After Effects error: File can not be opened.

Hopefully any AE master can help me solve my problem. Your help in this matter is greatly appreciated!