public Account ToModel() =>
 new Account(
     Id,
     Number,
     Name,
     Balances.Select(b => b.ToModel()),
     Positions.Select(p => p.ToModel()));
        public JObject ToJson()
        {
            JObject json = new JObject();

            json["block_identifier"] = BlockIdentifier.ToJson();
            json["balances"]         = Balances.Select(p => p.ToJson()).ToArray();
            if (Metadata != null && Metadata.ToJson() != null)
            {
                json["metadata"] = Metadata.ToJson();
            }
            return(json);
        }