private void increment(int bytes, int records) {
            this.bytes += bytes;
            this.records += records;
        }
Once we've detected that all of the {@link TopicPartition partitions} for the fetch have been handled, we
can then record the aggregated metrics values. This is done at the fetch level and on a per-topic basis.

@param partition {@link TopicPartition}
clients/src/main/java/org/apache/kafka/clients/consumer/internals/FetchMetricsAggregator.java