please explain this systemd service files question

[L.P.H. van Belle]

Hai, 
 
After days of searching why on a debian install samba and winbind fails, i did find this. 
in this folder :  SOURCE/packaging/systemd/
i notice the systemd service files with the following. 
 
for examplel this file : smb.service.in contains. 
[Unit]
Description=Samba SMB Daemon
Documentation=man:smbd(8) man:samba(7) man:smb.conf(5)
Wants=network-online.target
After=network.target network-online.target nmb.service winbind.service
 
[Service]
Type=notify
NotifyAccess=all
PIDFile=@PIDDIR@/smbd.pid
LimitNOFILE=16384
EnvironmentFile=- at SYSCONFDIR@/sysconfig/samba
ExecStart=@SBINDIR@/smbd --foreground --no-process-group $SMBDOPTIONS
ExecReload=/bin/kill -HUP $MAINPID
LimitCORE=infinity
@systemd_smb_extra@
 
[Install]
WantedBy=multi-user.target

 
 
Now my question what is @systemd_smb_extra@ and why is it there. 
 
Due to that, the service files on debian are modifies and this part is added: 
 

ExecStartPre=/bin/systemctl try-stop winbind.service
ExecStartPost=/bin/systemctl try-start winbind.service
Restart=on-failure
RestartSec=30s

resulting at the install :

Process: 2065 ExecStartPre=/bin/systemctl try-stop smbd.service (code=exited, status=1/FAILURE) 
because it does not understand try-stop ( or try-start ) 

The commands there :  systemctl try-stop  and systemctl try-start 
does not exist, so can someone explain this for me? 

Greetz, 

Louis