While reading an article devoted to the sparse self-attention, I came across a notation that was not very clear:
$$ Attend(X, S) = \Big( a(x_i, S_i) \Big)_{i∈{\{1,...,n}\}} $$
What means $\Big( \space \space \Big)_{i∈{\{1,...,n}\}}$ ?
It would be great to describe this in more detail.
Link to the article (page 4): https://arxiv.org/pdf/1904.10509.pdf
Please Help!
Thank You for your answers.