https://openjdk.java.net/ 
public interface java.lang.constant.Constable
  minor version: 0
  major version: 59
  flags: flags: (0x0601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT
  this_class: java.lang.constant.Constable
  super_class: java.lang.Object
{
  public abstract java.util.Optional<? extends java.lang.constant.ConstantDesc> describeConstable();
    descriptor: ()Ljava/util/Optional;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
    Signature: ()Ljava/util/Optional<+Ljava/lang/constant/ConstantDesc;>;
}
SourceFile: "Constable.java"