@Override
    public boolean isInitialized(TopicIdPartition topicIdPartition) {
        RemoteLogMetadataCache metadataCache = idToRemoteLogMetadataCache.get(topicIdPartition);
        return metadataCache != null && metadataCache.isInitialized();
    }
This class represents a store to maintain the {@link RemotePartitionDeleteMetadata} and {@link RemoteLogMetadataCache} for each topic partition.
storage/src/main/java/org/apache/kafka/server/log/remote/metadata/storage/RemotePartitionMetadataStore.java