1. Center for Human-Compatible Artificial Intelligence, Berkeley Institute for Data Science, University of California at Berkeley, Berkeley, CA, USA
2. School of Computing and Information Sciences, Willamette University, Salem, OR, USA
3. Department of Computer Science and Engineering, University of California at San Diego, La Jolla, CA, USA
4. Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Skellefteå, Sweden