public PartitionInfo partition(TopicPartition topicPartition) {
        return partitionsByTopicPartition.get(topicPartition);
    }
Get the metadata for the specified partition
@param topicPartition The topic and partition to fetch info for
@return The metadata about the given topic and partition, or null if none is found
clients/src/main/java/org/apache/kafka/common/Cluster.java