code: def _get_eligible_broker_pair(self, under_loaded_rg, eligible_partition):
          
          under_brokers = list(filter(
              lambda b: eligible_partition not in b.partitions,
              under_loaded_rg.brokers,
          ))
          over_brokers = list(filter(
              lambda b: eligible_partition in b.partitions,
              self.brokers,
          ))
  
          # Get source and destination broker
          source_broker, dest_broker = None, None
          if over_brokers:
              source_broker = max(
                  over_brokers,
                  key=lambda broker: len(broker.partitions),
              )
          if under_brokers:
              dest_broker = min(
                  under_brokers,
                  key=lambda broker: len(broker.partitions),
              )
          return (source_broker, dest_broker)
docs: Evaluate and return source and destination broker-pair from over-loaded
          and under-loaded replication-group if possible, return None otherwise.
  
          Return source broker with maximum partitions and destination broker with
          minimum partitions based on following conditions:-
          1) At-least one broker in under-loaded group which does not have
          victim-partition. This is because a broker cannot have duplicate replica.
          2) At-least one broker in over-loaded group which has victim-partition