Major API updates were made as in part 3 to address code review comments.
This revision focuses on Python wrappers of C++ iterators.
* Most getter/setter methods were reimplemented as attributes using PyGetSetDef.
* The naming of methods and attributes was fixed to follow the naming conventions
of the Blender Python API (i.e., lower case + underscores for methods and attributes,
and CamelCase for classes). The only irregular naming change is the following, to
better indicate the functionality:
- ChainingIterator: getVertex --> next_vertex
* In addition, some code clean-up was done in both C++ and Python. Also duplicated
definitions of predicate classes were removed.
