How to define parent/child relationship using Elastic.Clients.Elasticsearch C#

Question

I have this example written in "NEST library 7.6.1" of definition of Parent/Child relationships between elements.

"Product" is a parent.

"Stock", "Supplier", "Category" is a child of a Product

var createIndex = _ElasticClient.Indices.Create(_IndexName, x => x
     .Settings(s => s
                     .NumberOfReplicas(0)
                     .RefreshInterval(-1)
                     .NumberOfShards(5))
    .Index<BaseDocument>()
    .Map<BaseDocument>(m => m
        .RoutingField(r => r.Required())
        .AutoMap<Product>()
        .Properties<Product>(props => props
        //You can describe your properties below for Manual mapping
        .Text(s => s
           .Name(n => n.Name)
           .Analyzer("default")
           .Fields(pprops => pprops))
      )
                            .AutoMap<Category>()
                            .AutoMap<Supplier>()
                            .AutoMap<Stock>()
                            //You can add more join types here
                            .Properties(props => props
                                        .Join(j => j
                                            .Name(p => p.JoinField)
                                                //This is so important here. You can describe a relation that product is parent and the others is join type.
                                                .Relations(r => r
                                                .Join<Product>("category", "supplier", "stock")
                                                        )
                                        )
                                    )
                            )
);

I wonder how I can do this using the newest library for .NET/C# "Elastic.Clients.Elasticsearch"

I can't find any example that uses this latest library

Rest of the code:

public abstract class BaseDocument
{
    public virtual int Id { get; set; }
    public int Parent { get; set; }

    public JoinField JoinField { get; set; }

    public BaseDocument()
    {

    }
}
[ElasticsearchType(RelationName = "product")]
public class Product : BaseDocument
{
    [Keyword]
    public string Name { get; set; }

    public decimal Price { get; set; }
  
}
[ElasticsearchType(RelationName = "stock")]
public class Stock : BaseDocument
{
    [Keyword]
    public string Country { get; set; }

    public int Quantity { get; set; }
  
}
[ElasticsearchType(RelationName = "supplier")]
public class Supplier : BaseDocument
{
    [Keyword]
    public string SupplierDescription { get; set; }
  
}
[ElasticsearchType(RelationName = "category")]
public class Category : BaseDocument
{
    [Keyword]
    public string CategoryDescription { get; set; }
  
}```