Stereo Calibration for CharUco Boards?

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Are there any examples for calibrating two cameras simultaneously with CharUco Boards? I can do the single camera via these nice examples: https://docs.opencv.org/master/da/d13...

but was wondering what steps i might need to add if i wanted to calibrate two stereo cameras and get those other values (The T and the R between them)

Also total side-note, but on the "Interactive Camera Calibration Tutorial" they describe how to use the program, but where is the actual code? https://docs.opencv.org/trunk/d7/d21/...