I am currently using bandersnatch for mirroring PyPI and have encountered an issue regarding incremental synchronization. I want to set up my bandersnatch mirror to only sync new packages added to pypi.org. For packages that have been removed from pypi.org, do not delete these packages from the local mirror during synchronization. In short, only perform incremental backups without deleting any packages.

how to configure bandersnatch.conf to achieve this?