1. Department of Decision Sciences, Bocconi University, 20136 Milan, Italy;
2. The National Institute for Research in Computer Science and Automation (INRIA), École Normale Supérieure, Paris, France, 75012;
3. Bocconi Institute for Data Science and Analytics (BIDSA), 20136 Milan, Italy;
4. Department of Computer Science, Bioengineering, Robotics and Systems Engineering (DIBRIS), Università degli Studi di Genova, 16145 Genova, Italy;
5. Laboratory for Computational and Statistical Learning (LCSL), Massachusetts Institute of Technology, Cambridge, Massachusetts 02139;
6. Istituto Italiano di Tecnologia, 16163 Genova, Italy