COCO export is very memory inefficient.

[jrdalenberg]

When I try to export a dataset to COCO (ds.export(style='coco')) with 75k images (200-800kb), each containing a single segmentation, the export function uses around 128GB RAM and 60GB swap.

I assume that images are loaded but not released from memory when coco annotations are generated.

I am using python 3.8.18
opencv-python==4.5.3.56
imantics 3cd6526