/lib/partman/choose_method/ is in ubiquity 2.10.16.
This file is owned by root:root, with mode 0o755.
..
/lib/partman/choose_method/25filesystem/
/lib/partman/choose_method/25filesystem/choices
/lib/partman/choose_method/25filesystem/do_option
/lib/partman/choose_method/40swap/
/lib/partman/choose_method/40swap/choices
/lib/partman/choose_method/40swap/do_option
/lib/partman/choose_method/45biosgrub/
/lib/partman/choose_method/45biosgrub/choices
/lib/partman/choose_method/45biosgrub/do_option
/lib/partman/choose_method/45efi/
/lib/partman/choose_method/45efi/choices
/lib/partman/choose_method/45efi/do_option
/lib/partman/choose_method/70dont_use/
/lib/partman/choose_method/70dont_use/choices
/lib/partman/choose_method/70dont_use/do_option
/lib/partman/choose_method/priority
/lib/partman/choose_method/question