[NTG-context] MetaFun: Rotate picture without rotating labels

Dear list, In the MWE below I would like py to be px rotated by 90 degrees but the labels should not be rotated.  Is it possible? Cheers, Henri --- \startMPpage   path p ; p := origin .. (2,1) .. (3,0) .. (2,-1) .. (-2,1) .. (-3,0) .. (-2,-1) .. cycle ;   picture px, py ;   px := image (     draw p scaled 6 ;     label("$+$",(+10,0));     label("$-$",(-10,0));   ) ;   py := px rotated 90 ;   draw px ;   draw py ; % meh :/ \stopMPpage