/usr/share/doc/diveintopython/examples/plural-rules.en is in diveintopython 5.4-2ubuntu2.
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 8 9 10 11 12 13 14 15 16 17 18 19 | ^(sheep|deer|fish|moose|aircraft|series|haiku)$ ($) \1
[ml]ouse$ ouse$ ice
child$ $ ren
booth$ $ s
foot$ oot$ eet
ooth$ ooth$ eeth
l[eo]af$ af$ aves
sis$ sis$ ses
^(hu|ro)man$ $ s
man$ man$ men
^lowlife$ $ s
ife$ ife$ ives
eau$ $ x
^[dp]elf$ $ s
lf$ lf$ lves
[sxz]$ $ es
[^aeioudgkprt]h$ $ es
(qu|[^aeiou])y$ y$ ies
$ $ s
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