title: Can not retrieve thumbnailLink from google drive API
body: <p>I am trying to get the thumbnailLink from files from a shared drive using python and the google Drive API, however, the file information does not include the thumbnailLink (although for most files the hasThumbnail field, which i do get as a field for the file, has a value of true)</p>
  
  <p>I have looked around a lot and none of the solutions i have found seem to work (although this is my first python project as well as my first google drive api project, so i might just be ignorant of what i am doing)</p>
  
  <p>What i have tried:
  - setting the scope to '<a href="https://www.googleapis.com/auth/drive" rel="nofollow noreferrer">https://www.googleapis.com/auth/drive</a>' (was ..drive.metadata.readonly before)
  - using a wildcard as such: <code>results = drive.files().list(pageSize=10, fields="*",blablabla...)</code>. If i for instance try fields="thumbnailLink" it doesn't find any files.
  - after getting the list, i tried using the id of each file from that list to do <code>file = service.files().get(fileId=item_id, supportsAllDrives=True, fields="*").execute()</code> but the same happens, i have many fields including the hasThumbnail field which is set to true, yet no thumbnail link.
  - i tried using the "Try this API" console on the official website, where i did in fact get the thumbnailLink!! (with the same parameters as above). So i do not understand why this is missing when requested from my application.</p>
  
  <p>Edit (code):
  i have one method like so</p>
  
  <pre><code>SCOPES = ['https://www.googleapis.com/auth/drive']
  
  def getDrive():
      """Shows basic usage of the Drive v3 API.
      Prints the names and ids of the first 10 files the user has access to.
      """
      creds = None
      # The file token.pickle stores the user's access and refresh tokens, and is
      # created automatically when the authorization flow completes for the first
      # time.
      if os.path.exists('token.pickle'):
          with open('token.pickle', 'rb') as token:
              creds = pickle.load(token)
      # If there are no (valid) credentials available, let the user log in.
      if not creds or not creds.valid:
          if creds and creds.expired and creds.refresh_token:
              creds.refresh(Request())
          else:
              flow = InstalledAppFlow.from_client_secrets_file(
                  'credentials.json', SCOPES)
              creds = flow.run_local_server(port=53209)
          # Save the credentials for the next run
          with open('token.pickle', 'wb') as token:
              pickle.dump(creds, token)
  
      service = build('drive', 'v3', credentials=creds)
      return service
  </code></pre>
  
  <p>then i call it from here and also get the files:</p>
  
  <pre><code>def getFiles(request):
      drive = getDrive()
      # Call the Drive v3 API
      results = drive.files().list(
          pageSize=10, fields="*", driveId="blabla", includeItemsFromAllDrives=True, corpora="drive", supportsAllDrives=True).execute()
  
      items = results.get('files', [])
      getItems = []
      for item in items:
          item_id = item['id']
          getItems.append(drive.files().get(fileId=item_id, supportsAllDrives=True, fields="*").execute())
      if not items:
          print('No files found.')
      else:
          print('Files:')
          print(getItems)
          for item in items:
              # print(u'{0} ({1})'.format(item['name'], item['id']))
              print(item)
  
      return render(request, "index.html", {'files': getItems})
  </code></pre>
  
  <p>Also, yes, i do use a service account, i can retrieve all the files i need, just not the thumbnailLink.</p>
  
  <p>I don't think it makes sense to call list() and then also get() but i had read that the problem could be solved through the get() method, which in my case did not work.</p>