Previously, I used the NEST library to use Elasticsearch. This is now deprecated. I have implemented the recommended Elastic.Client.Elasticsearch. However, this library does not recognise the Attachment class.
How do I deal with this problem?

using System;
//using Nest;
using Elastic.Clients.Elasticsearch;

namespace Contracts
{
    public class ElasticDocument
    {
        public int ID { get; set; }

        public string Name { get; set; } = string.Empty;

        public int Date { get; set; }

        public DateTime Modified { get; set; }

        public string Content { get; set; } = string.Empty;

        // class Attachment is unknown in Elastic.Clients.Elasticsearch
        public Attachment Attachment { get; set; }
    }
}