System information (version)

• OpenCV => 4.5.2
• Operating System / Platform => Ubuntu 18.05
• Compiler => python

Detailed description

in your documentation there is an example of a fancy checkerboard with markers etc under findChessboardCornersSB() (see here). This pattern works particularily well in my experiments but gen_pattern can't create it. It would be really helpfull if you could add it.