From BlenderWiki
2013/02/24: Hello, I have read the presented specification of the Python node classes. Still the key point is unclear: which is the function that a Python node has to implement, to perform its basic task (i.e. read the input data and deliver the output data)? In 2.4 PyNodes it was the _call_ function, but I have found nothing like this in this spec... [Witold Jaworski]
