public Envelope(
     [JsonProperty("@type")] string typeAnnotation,
     [JsonProperty("instanceSetHistory")] InstanceSetHistory instanceSetHistory)
     : this(instanceSetHistory)
 {
     if (typeAnnotation != TypeAnnotation)
     {
         throw new FormatException("Missing type annotation: " + TypeAnnotation);
     }
 }
 public Envelope(
     InstanceSetHistory instanceSetHistory)
 {
     this.InstanceSetHistory = instanceSetHistory;
 }