/usr/share/debhelper/autoscripts/prerm-metainit is in dh-metainit 0.0.5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 | if [ -x "/etc/init.d/#SCRIPT#" ]; then
	if [ -x "`which invoke-rc.d 2>/dev/null`" ]; then
		invoke-rc.d #SCRIPT# stop || #ERROR_HANDLER#
	else
		/etc/init.d/#SCRIPT# stop || #ERROR_HANDLER#
	fi
fi
 |