I realized today that it will not be possible to implement getter/setter functionality easily for our Freestyle API. The reason is that Python does not support function overloading as-is. It is possible to 'fake' overloading by taking a general argument object and count the number of arguments in the object (rgbTuple_setCol in Blender's API is a good example of how to go about it).
For the time being, we'll get around that problem. The tangible effect of that constraint is that all API setter functions return a 'None' PyObject, instead of returning an integer status code. It is important to note that this problem is due to Freestyle's API being C++ in nature. Fortunately, this shouldn't really impact the usage of the API.
If the Blender Python group wants me to correct that, I'll be able to do it. It is just going to take me quite some time correcting it, writing support functions for methods having different types of arguments.
IMPORTANT: The setters functions' names were normalized due to constant confusion regarding capitalization. All the function names start with set... instead of Set.... This convention was changed all throughout Freestyle. To use Freestyle as an external renderer, the SWIG library MUST be regenerated.
Maxime Curioni