About Pre-processed data surreal details.

[NeaRBrotheR]

In the data folder,'surreal_val_idxs.npy' have so much key item.
This file include the keys : ['betas', 'bones', 'c2ws', 'cam_idxs', 'cyls', 'ext_scale', 'focals', 'gt_poses', 'img_paths', 'img_shape', 'imgs', 'kp3d', 'kp_idxs', 'masks', 'pose_scale', 'rest_pose', 'sampling_masks', 'skts']
I wonder like to know the detail of these keys.
Like what do they mean individually.

And how do i create a file like surreal_val_idxs.npy on my own data?