Received: 24 November 2020
Accepted: 18 April 2021
First Online: 29 April 2021
: No ethical approval was required for this review.
: Not applicable
: Roshan Patel, Caitlin Kemp, Muneebah Hafejee, Nicholas Peckham, Vageesh Jain, Gerry McCann and Susil Pallikadavath declare that they have no conflicts of interest relevant to the content of this review.