/lib/udev/rules.d/71-power-switch-proliant.rules is in udev 229-4ubuntu4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | ACTION!="remove", SUBSYSTEM=="input", KERNEL=="event*", SUBSYSTEMS=="platform", KERNELS=="gpio_keys.6|soc:gpio_keys", PROGRAM="/bin/cat /proc/device-tree/model", RESULT=="HP ProLiant m400 Server Cartridge", TAG+="power-switch"
ACTION!="remove", SUBSYSTEM=="input", KERNEL=="event*", SUBSYSTEMS=="platform", KERNELS=="gpio_keys.12", ATTRS{keys}=="116", PROGRAM="/bin/cat /proc/device-tree/model", RESULT=="HP ProLiant m800 Server Cartridge", TAG+="power-switch"
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