python interface: extract out print_arg_in_call
python interface: extract out print_arg_in_call

This removes some duplication in isl_class::print_method and
makes it slightly easier to read.

Signed-off-by: Sven Verdoolaege <e5350bbed4977f5eb8ae1dc6abd9ae59d21ace75@kotnet.org>

BenzoSM/isl,PollyLabs/isl,UBERTC/isl,BenzoSM/isl,PollyLabs/isl,nicolasvasilache/isl,PollyLabs/isl,tobig/isl,Distrotech/isl,inducer/isl-mirror,nicolasvasilache/isl,Meinersbur/isl,Meinersbur/isl,tobig/isl,Distrotech/isl,inducer/isl-mirror,UBERTC/isl,PollyLabs/isl,nicolasvasilache/isl,tobig/isl,Meinersbur/isl,UBERTC/isl,nicolasvasilache/isl,Distrotech/isl,BenzoSM/isl,Distrotech/isl,BenzoSM/isl,inducer/isl-mirror,UBERTC/isl,inducer/isl-mirror,Distrotech/isl,BenzoSM/isl,tobig/isl,inducer/isl-mirror,nicolasvasilache/isl,Meinersbur/isl,PollyLabs/isl