What "sid" and "config" means in LMDB file?

[yinkaaiwu]

Hello,
In LMDB, value is look like:
Data(pos=[98, 3], cell=[1, 3, 3], atomic_numbers=[98], natoms=98, tags=[98], edge_index=[2, 4581], cell_offsets=[4581, 3], fixed=[98], sid=0, config=1)

What "sid" and "config" means? And how to find system_id in LMDB?