# File lib/snmp/pdu.rb, line 275
    def trap_oid
      varbind = @varbind_list[1]
      if varbind && (varbind.name == SNMP_TRAP_OID_OID)
        return varbind.value
      else
        raise InvalidTrapVarbind, "Expected snmpTrapOID.0, found " + varbind.to_s
      end
    end