Thinking about it a bit more, I really would prefer get_range_argument not to steal a reference.  If I'm reading a bit of C code and encounter something like:

  obj = transform(obj);
  if (obj == NULL) ...

my hindbrain immediately starts fretting that something's wrong, and I have to go and ferret out the definition of 'transform' to be sure.  In contrast, patterns like:

  temp = transform(obj);
  Py_DECREF(obj);
  obj = temp;
  if (obj == NULL) ...

are so common and familiar in the Python codebase that they don't raise the same sort of red flag.