CvPythonExtensions What?

There are numerous references to CvPythonExtensions in .py files but i can neither find it or find out what it is about. any help from the pros would be awesome! TY

There's no actual CvPythonExtensions file. Basically importing from CvPythonExtensions is how all the base classes supplied by the game are accessed. If you search the forum for CvPythonExtensions you'll come across a few other topics asking the same question such as this one from nearly 3 years ago.