/lib/udev/rules.d/80-docker.io.rules is in docker.io 17.12.1-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 | # hide docker's loopback devices from udisks, and thus from user desktops
SUBSYSTEM=="block", ENV{DM_NAME}=="docker-*", ENV{UDISKS_PRESENTATION_HIDE}="1", ENV{UDISKS_IGNORE}="1"
SUBSYSTEM=="block", DEVPATH=="/devices/virtual/block/loop*", ATTR{loop/backing_file}=="/var/lib/docker/*", ENV{UDISKS_PRESENTATION_HIDE}="1", ENV{UDISKS_IGNORE}="1"
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