https://github.com/oracle/graal: GraalVM is an ecosystem for compiling and running applications written in multiple languages. GraalVM removes the isolation between programming languages and enables interoperability in a shared runtime. 
class org.graalvm.polyglot.proxy.ProxyDuration$1 implements org.graalvm.polyglot.proxy.ProxyDuration
  minor version: 0
  major version: 59
  flags: flags: (0x0020) ACC_SUPER
  this_class: org.graalvm.polyglot.proxy.ProxyDuration$1
  super_class: java.lang.Object
{
  private final java.time.Duration val$duration;
    descriptor: Ljava/time/Duration;
    flags: (0x1012) ACC_PRIVATE, ACC_FINAL, ACC_SYNTHETIC

  void <init>(java.time.Duration);
    descriptor: (Ljava/time/Duration;)V
    flags: (0x0000) 
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // org.graalvm.polyglot.proxy.ProxyDuration$1 this
         0: .line 69
            aload 0 /* this */
            aload 1
            putfield org.graalvm.polyglot.proxy.ProxyDuration$1.val$duration:Ljava/time/Duration;
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // org.graalvm.polyglot.proxy.ProxyDuration$1 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/graalvm/polyglot/proxy/ProxyDuration$1;
    MethodParameters:
              Name  Flags
      val$duration  final

  public java.time.Duration asDuration();
    descriptor: ()Ljava/time/Duration;
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // org.graalvm.polyglot.proxy.ProxyDuration$1 this
         0: .line 72
            aload 0 /* this */
            getfield org.graalvm.polyglot.proxy.ProxyDuration$1.val$duration:Ljava/time/Duration;
            areturn
        end local 0 // org.graalvm.polyglot.proxy.ProxyDuration$1 this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lorg/graalvm/polyglot/proxy/ProxyDuration$1;
}
SourceFile: "ProxyDuration.java"
EnclosingMethod: org.graalvm.polyglot.proxy.ProxyDuration.from:(Ljava/time/Duration;)Lorg/graalvm/polyglot/proxy/ProxyDuration;
NestHost: org.graalvm.polyglot.proxy.ProxyDuration
InnerClasses:
  org.graalvm.polyglot.proxy.ProxyDuration$1