Starting with a link to a folder I'm trying to get info on all Docs/Slides/Sheets in that folder, the subfolders (and subfolders of subfolders).

With some online searching I finally got some code that will find ALL FILES, but I need to modify it to ONLY find Docs, Slides, and Sheets. What would be the best way to do that? 

Here's the code I'm currently using:

```
function generateFolderTree(my_id) {
  var parentFolder = DriveApp.getFolderById(my_id);
  var f = parentFolder.getFiles();
  Logger.log(f.next().getName())

  getChildFolders(parentFolder);
}

function getChildFolders(parent) {
  var childFolders = parent.getFolders();
  while (childFolders.hasNext()) {
    var childFolder = childFolders.next();
    var files = childFolder.getFiles();
    while (files.hasNext()) { 
      Logger.log(files.next().getName()); // Print list of files inside the folder
    }
    getChildFolders(childFolder); // Recursive call for any sub-folders
  }
}

```