[NTG-context] What's the current method for using a variable font in Context and Metapost?

I haven't been able to find working examples. Here is some sample code. I would really like to be able to use the light variation of this DIN-like font. \usemodule[fonts-variable] \definefontfamily [mainface] [ss] [bahnschrift] \setupbodyfont[mainface] \starttext \ss 123456789 Wild! \medskip \startMPcode picture pic; pic := thelabel("This is in Metafont 0123456789", (0, 0)); draw pic; \stopMPcode \stoptext