/usr/share/fish/completions/rfkill.fish is in fish-common 2.4.0-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | complete -c rfkill -xa 'block unblock list event help' -n 'not __fish_seen_subcommand_from block unblock list event help'
complete -c rfkill -n '__fish_seen_subcommand_from block unblock list' -d 'device group' -xa "all wifi wlan bluetooth uwb ultrawideband wimax wwan gps fm (rfkill list | tr : \t)"
complete -c rfkill -l version -d 'Print version'
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