DHCP Relay on EX3400

How do you configure DHCP-Relay on the new EX3400 switches (version: 15.1X53-D55.5)?  It used to be as simple as this:

set forwarding-options helpers bootp server 10.100.134.10
set forwarding-options helpers bootp interface vlan.10
set forwarding-options helpers bootp interface vlan.20

Please help.  I am trying to configure a new switch.  A configuration example based on the above would be great.

Thank you!!