1. Spotify Ltd, 4 Savoy Place, London WC2N 6AT, United Kingdom; Institute of Mathematics EPFL, CH-1015 Lausanne, Switzerland and DataShape, Inria, Faculté des Sciences d’Orsay, Université Paris-Saclay F-91405 Orsay, France.
2. Department of Mathematical Sciences, Durham University, Durham DH1 3LE, United Kingdom, and Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom.
3. Spotify Ltd, 4 Savoy Place, London WC2N 6AT, United Kingdom.
4. Mathematical Institute, University of Oxford, Oxford OX2 6GG, United Kingdom.