How does the summarization work?

[Hellisotherpeople]

This looks like it's doing abstractive summarization, but occasionally it can do pure extractive summarization.

Can you confirm - and explain the exact methodology used in the summarization module?

[artitw]

It’s abstractive and based on the pre-training transformers like BERT. For more details, see https://arxiv.org/abs/1905.03197

For an introduction to transformers, see https://youtu.be/iRT6C7R7NHk