/lib/partman/storage_device/00cancel/do_option is in ubiquity 18.04.14.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 | #!/bin/sh -e
. /lib/partman/lib/base.sh
dev="$2"
cd $dev
exit 100
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