Something

modparam("nathelper", "sipping_bflag", 6)
modparam("nathelper", "natping_interval", 5)
modparam("nathelper", "received_avp", "$avp(i:3)")
modparam("nathelper", "sipping_from", "sip:pinger@sip.demo.com")
modparam("nathelper", "ping_nated_only", 1)