Mostly I made the code more consist with the other methods in this file, and
also made `using_list` to be more literal (i.e. not to include tuples as
well)

Before we used to use the variables `using_list`, `using_tuple`, but I feel
is much more clean if we do not rely on those variables that are meant only
for re-formating the output

Following olivier's suggestion, I refractored the code that retransforms
the output in either a list or tuple

We are not importing scan directly anymore

the previous code returned list of tuples (not 100% sure why - I guess is a
python thing). This makes sure we are dealing with a list of variables.

Fix tests sandbox scan

There are two things to wait for :
 1) Fix bugs in sandbox scan
 2) Add more restriction to scan which would simplify this test

avoiding name collision and other things

also make sure it has the right sign