code: @SuppressWarnings("unchecked")
    public static <Message> Descriptor.Properties.Property<Message, PartitionKeyStrategy<Message>> partitionKeyStrategy() {
      return PARTITION_KEY_STRATEGY;
    }
docs: A PartitionKeyStrategy produces a key for each message published to a Kafka topic.
  
  The key is used to determine on which topic's partition a message is published. It is guaranteed that messages
  with the same key will arrive to the same partition, in the order they are published.