https://www.graalvm.org/ 
public abstract class com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference extends java.lang.ref.PhantomReference<java.lang.Object>
  minor version: 0
  major version: 59
  flags: flags: (0x0421) ACC_PUBLIC, ACC_SUPER, ACC_ABSTRACT
  this_class: com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference
  super_class: java.lang.ref.PhantomReference
{
  private final java.lang.Object reference;
    descriptor: Ljava/lang/Object;
    flags: (0x0012) ACC_PRIVATE, ACC_FINAL

  private boolean released;
    descriptor: Z
    flags: (0x0002) ACC_PRIVATE

  static final boolean $assertionsDisabled;
    descriptor: Z
    flags: (0x1018) ACC_STATIC, ACC_FINAL, ACC_SYNTHETIC

  static void <clinit>();
    descriptor: ()V
    flags: (0x0008) ACC_STATIC
    Code:
      stack=1, locals=0, args_size=0
         0: .line 325
            ldc Lcom/oracle/graal/python/runtime/AsyncHandler;
            invokevirtual java.lang.Class.desiredAssertionStatus:()Z
            ifne 1
            iconst_1
            goto 2
      StackMap locals:
      StackMap stack:
         1: iconst_0
      StackMap locals:
      StackMap stack: int
         2: putstatic com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference.$assertionsDisabled:Z
            return
      LocalVariableTable:
        Start  End  Slot  Name  Signature

  public void <init>(java.lang.Object, java.lang.Object, com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer);
    descriptor: (Ljava/lang/Object;Ljava/lang/Object;Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=3, locals=4, args_size=4
        start local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
        start local 1 // java.lang.Object referent
        start local 2 // java.lang.Object reference
        start local 3 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer sharedFinalizer
         0: .line 330
            aload 0 /* this */
            aload 1 /* referent */
            aload 3 /* sharedFinalizer */
            getfield com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer.queue:Ljava/lang/ref/ReferenceQueue;
            invokespecial java.lang.ref.PhantomReference.<init>:(Ljava/lang/Object;Ljava/lang/ref/ReferenceQueue;)V
         1: .line 331
            getstatic com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference.$assertionsDisabled:Z
            ifne 2
            aload 2 /* reference */
            ifnonnull 2
            new java.lang.AssertionError
            dup
            invokespecial java.lang.AssertionError.<init>:()V
            athrow
         2: .line 332
      StackMap locals: com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference java.lang.Object java.lang.Object com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer
      StackMap stack:
            aload 0 /* this */
            aload 2 /* reference */
            putfield com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference.reference:Ljava/lang/Object;
         3: .line 333
            aload 3 /* sharedFinalizer */
            aload 0 /* this */
            invokestatic com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference.addLiveReference:(Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer;Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer$FinalizableReference;)V
         4: .line 334
            return
        end local 3 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer sharedFinalizer
        end local 2 // java.lang.Object reference
        end local 1 // java.lang.Object referent
        end local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
      LocalVariableTable:
        Start  End  Slot             Name  Signature
            0    5     0             this  Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer$FinalizableReference;
            0    5     1         referent  Ljava/lang/Object;
            0    5     2        reference  Ljava/lang/Object;
            0    5     3  sharedFinalizer  Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer;
    MethodParameters:
                 Name  Flags
      referent         
      reference        
      sharedFinalizer  

  private static void addLiveReference(com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer, com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference);
    descriptor: (Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer;Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer$FinalizableReference;)V
    flags: (0x000a) ACC_PRIVATE, ACC_STATIC
    Code:
      stack=3, locals=2, args_size=2
        start local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer sharedFinalizer
        start local 1 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference ref
         0: .line 342
            aload 0 /* sharedFinalizer */
            getfield com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer.liveReferencesSet:Ljava/util/concurrent/ConcurrentMap;
            aload 1 /* ref */
            aload 1 /* ref */
            invokeinterface java.util.concurrent.ConcurrentMap.put:(Ljava/lang/Object;Ljava/lang/Object;)Ljava/lang/Object;
            pop
         1: .line 343
            return
        end local 1 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference ref
        end local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer sharedFinalizer
      LocalVariableTable:
        Start  End  Slot             Name  Signature
            0    2     0  sharedFinalizer  Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer;
            0    2     1              ref  Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer$FinalizableReference;
    RuntimeVisibleAnnotations: 
      com.oracle.truffle.api.CompilerDirectives$TruffleBoundary()
    MethodParameters:
                 Name  Flags
      sharedFinalizer  
      ref              

  public final java.lang.Object getReference();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0011) ACC_PUBLIC, ACC_FINAL
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
         0: .line 350
            aload 0 /* this */
            getfield com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference.reference:Ljava/lang/Object;
            areturn
        end local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer$FinalizableReference;

  public final boolean isReleased();
    descriptor: ()Z
    flags: (0x0011) ACC_PUBLIC, ACC_FINAL
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
         0: .line 354
            aload 0 /* this */
            getfield com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference.released:Z
            ireturn
        end local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer$FinalizableReference;

  public final void markReleased();
    descriptor: ()V
    flags: (0x0011) ACC_PUBLIC, ACC_FINAL
    Code:
      stack=2, locals=1, args_size=1
        start local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
         0: .line 362
            aload 0 /* this */
            iconst_1
            putfield com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference.released:Z
         1: .line 363
            return
        end local 0 // com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    2     0  this  Lcom/oracle/graal/python/runtime/AsyncHandler$SharedFinalizer$FinalizableReference;

  public abstract com.oracle.graal.python.runtime.AsyncHandler$AsyncAction release();
    descriptor: ()Lcom/oracle/graal/python/runtime/AsyncHandler$AsyncAction;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
}
Signature: Ljava/lang/ref/PhantomReference<Ljava/lang/Object;>;
SourceFile: "AsyncHandler.java"
NestHost: com.oracle.graal.python.runtime.AsyncHandler
InnerClasses:
  public abstract AsyncAction = com.oracle.graal.python.runtime.AsyncHandler$AsyncAction of com.oracle.graal.python.runtime.AsyncHandler
  public SharedFinalizer = com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer of com.oracle.graal.python.runtime.AsyncHandler
  public abstract FinalizableReference = com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer$FinalizableReference of com.oracle.graal.python.runtime.AsyncHandler$SharedFinalizer
  public abstract TruffleBoundary = com.oracle.truffle.api.CompilerDirectives$TruffleBoundary of com.oracle.truffle.api.CompilerDirectives