code: public static <E> PartitionKey partitionKeyForEntity(PartitionStrategy strategy,
        E entity, EntityAccessor<E> accessor) {
      return partitionKeyForEntity(strategy, entity, accessor, null);
    }
docs: <p>
  Construct a partition key for the given entity.
  </p>
  <p>
  This is a convenient way to find the partition that a given entity is
  written to, or to find a partition using objects from the entity domain.
  </p>