code: def find_matching_link(self, mode, group, addr):
          
          found_rec = None
          mode_test = None
          if mode.lower() in ['c', 'r']:
              link_group = int(group)
              link_addr = Address(addr)
              for mem_addr in self:
                  rec = self[mem_addr]
                  if mode.lower() == 'r':
                      mode_test = rec.control_flags.is_controller
                  else:
                      mode_test = rec.control_flags.is_responder
                  if (mode_test and
                          rec.group == link_group and
                          rec.address == link_addr):
                      found_rec = rec
          return found_rec
docs: Find a matching link in the current device.
  
          Mode: r | c is the mode of the link in the linked device
                This method will search for a corresponding link in the
                reverse direction.
          group: All-Link group number
          addr:  Inteon address of the linked device