code: def interface(self):
          
          nics = set([nic.get('nicid') for nic in \
              getattr(self.engine, 'snmp_interface', [])])
          return [self.engine.interface.get(nic) for nic in nics]
docs: Return a list of physical interfaces that the SNMP
          agent is bound to.
          
          :rtype: list(PhysicalInterface)