With this bot, we’ll find the number of faces in a photo that is tweeted at us, and respond back with what emotions the faces are expressing, using the Google Cloud Vision API.
The Google Cloud Vision API is worth exploring, and you'll need to create an account before this lesson: https://cloud.google.com/vision/
I am currently getting a TypeError: vision.detectFaces is not a function
I am making a guess that the api has changed since the tutorial was posted. When I find a solution I will post it here and submit a pull request on github. For now just an FYI :)