/lib/cryptsetup/checks/swap is in cryptsetup 2:1.4.1-2ubuntu4.
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 | #!/bin/sh
echo "WARNING: The check script $0 is depreciated. Please use check script blkid instead." >&2
/lib/cryptsetup/checks/blkid "$1" "swap"
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