AFAIK, the "central algorithm" is based on a convolutional neural network.
What software you use the implement the algorithm doesn't really matter as long as it has the necessary features.
https://www.microsoft.com/en-us/cognitive-toolkit/blog/2017/09/microsoft-facebook-create-open-ecosystem-ai-model-interoperability/
https://www.cnbc.com/2017/05/09/twitter-using-deep-learning-ai-to-rank-tweets.html
https://www.tensorflow.org/