Transforming a stl in gts surface

Hello everyone!

I have a stl geometry that I can easily import to yade using ymport.stl.
My problem is that I want to use this geometry as a predicate. I have read in some topics that to do this, a good idea should be to transform my stl in a gts surface so that I can use it as a predicate. The point is that stl2gts command - that used to do this - is not working anymore (NameError: name 'stl2gts' is not defined).
I would like to know if there is another command that do this conversion for me (stl to gts) or if there is another way to use my stl geometry as a predicate.

Many thanks,

Abimael.