Can't unlock bootdriver htc desire 728 dual sim solution

[Fernon]

Can't unlock bootloader Htc desire 728 dual sim solution
showing this error
C:\adb>fastboot devices
LC6BAB805661 fastboot

C:\adb>fastboot oem get_identifier_token
...
FAILED (remote: unknown command)
finished. total time: 0.004s

C:\adb>