I just removed this part of the code because it anyway just printed duplicate
information. I think this was a leftover from TFD's code for possibly nested
functions that is not necessary for the simpler numeric fragment supported by
Fast Downward.
I don't know what the intention of this was (the translator change to support
action costs was done by either Silvia or the Temporal Fast Downward team, I
think), but I'm in favour of the minimal fix: just change dump.
The dump method of PrimitiveNumericExpression expects the arguments to be some
kind of term objects but they are strings.
(try ./normalize.py
../../benchmarks/elevators-opt08-strips/{p01-domain,p01}.pddl to trigger the error)
I did not directly fix this in the dump method because I am not sure whether the
arguments shouldn't indeed better be 'real' objects.