Need help for digital.constellation_decoder_cb in release 3.5.0

I noticed dramatic changes in the 3.5.0 release in the generation of the
constellation points of digital modulations. So, if the easy part is to
again modify the source code to match my needs, i need some help in
using the new block :


instead of

I usually used the last one where /arg1/ is a list containing the
complex values of a generic digital modulation and /arg2/ is the symbol
mapping (Gray Coding for instance). Which blocks do i need to put
together to get the same result ?

Regards, Arturo