https://openjdk.java.net/ 
public interface sun.invoke.WrapperInstance
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: sun.invoke.WrapperInstance
  super_class: java.lang.Object
{
  public abstract java.lang.invoke.MethodHandle getWrapperInstanceTarget();
    descriptor: ()Ljava/lang/invoke/MethodHandle;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT

  public abstract java.lang.Class<?> getWrapperInstanceType();
    descriptor: ()Ljava/lang/Class;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    Signature: ()Ljava/lang/Class<*>;
}
SourceFile: "WrapperInstance.java"