Properly expect custom handlers to be specified with return type.
Properly expect custom handlers to be specified with return type.

ene-ilies/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware,ene-ilies/vi-firmware,mgiannikouris/vi-firmware,ene-ilies/vi-firmware,openxc/vi-firmware,mgiannikouris/vi-firmware,openxc/vi-firmware,ene-ilies/vi-firmware