About new feature option AuthorizedPrincipalsFile in openssh5.6

[lei yuan]

hi,all

i've read the openssh5.6 new feature document about new option
AuthorizedPrincipalsFile,and tried to config the sshd_config for a lot
times,but still not succeed.
maybe i am still ambiguously about the document's meaning.
The main problem is i don't know what's the content(or file format) in the
file that specifed by the  AuthorizedPrincipalsFile option.
could you give me a example file of AuthorizedPrincipalsFile's specify file
or explains the file content in details ?
i would be appreciated if you could give me some help.