From the FT this morning:
"The third [ETF being launched] resembles a traditional hedge fund offering a “long-short” strategy, buying stocks of companies active in online retailing while betting against bricks-and-mortar chains. All three will track bespoke indices managed by ProShares."
https://www.ft.com/content/dea75884-65bc-11e7-9a66-93fb352ba1fe
It would be a fun exercise to match this strategy on Quantopian.