instance segmentation

Thank you for your wonderful work. The open Images Dataset V5 was just released, which contained instance segmentation. Would you mind update the package to support download of instance mask?

Thank you again for your work.

The issue names no files, tests, or entry points. Start by locating the package’s existing Open Images download and annotation handling, then compare it with the V5 instance-segmentation data. Done means the package can download instance masks, with a test or verification step demonstrating that behavior.

Written by the indexing model from the issue text.