[Some "xmlns","m","http://www.w3.org/1998/Math/MathML" ;
Some "xmlns","helm","http://www.cs.unibo.it/helm" ;
Some "xmlns","xlink","http://www.w3.org/1999/xlink"
- ] (print_mpres pres)
+ ] (Xml.xml_nempty ~prefix "mstyle" [None, "mathvariant", "normal"] (print_mpres pres))
>]