tootle-linux-client/src/API/Attachment.vala

public class Tootle.API.Attachment : Entity {

    public string id { get; set; }
    public string kind { get; set; }
    public string url { get; set; }
    public string? description { get; set; }
    public string? _preview_url { get; set; }
    public string? preview_url {
    	set { this._preview_url = value; }
    	get { return (this._preview_url == null || this._preview_url == "") ? url : _preview_url; }
	}

}