/lib/partman/choose_method/45efi/choices is in ubiquity 2.18.7.
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 9 10 11 12 | #!/bin/sh
. /usr/share/debconf/confmodule
dev=$1
id=$2
[ -e /var/lib/partman/efi ] || exit 0
db_metaget partman-efi/text/efi description
printf "efi\t${RET}\n"
|