I tried to find some more information about this. Seems like the article is referring to a request that was made in March 2016 [1] by the Swedish Prosecution Authority.

Their timeline of "The Assange Matter" in Swedish is a bit more detailed [2]

[1] (English) https://www.aklagare.se/nyheter-press/for-media/the-assange-...

[2] (Swedish) https://www.aklagare.se/nyheter-press/for-media/assangearend...