What does the pkl file contain in training with Matterport3D?

[Ulricall]

I'm trying to train my own network following the tutorial in /training. The dataset is Matterport3D. I noticed an example json file about this dataset that includes "{"meta_data": "Matterport3D/data/SN83YJsR3w2/SN83YJsR3w2/meta/4a87c9150e8442a1b8abc51ed5073ca0_i1_4.pkl"}". I downloaded the dataset but did not find a pkl file, only many zip files.