Opencv python摄像机标定:objp矩阵。

This is the camera calibration code as on the opencv python docs. I want to know how objp[:,:2] = np.mgrid[0:7,0:6].T.reshape(-1,2) works. What does reshape (-1,2) do? I tried to change the values in this line of code but got errors. Can someone explain how this works and why only these numbers would work? This is the camera calibration code as on the o