https://www.graalvm.org/ 
public class com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS
  minor version: 0
  major version: 59
  flags: flags: (0x0021) ACC_PUBLIC, ACC_SUPER
  this_class: com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS
  super_class: java.lang.Object
{
  private com.oracle.truffle.js.test.interop.TargetTypeMappingTest$JsonObject jsonObject;
    descriptor: Lcom/oracle/truffle/js/test/interop/TargetTypeMappingTest$JsonObject;
    flags: (0x0002) ACC_PRIVATE

  public void <init>();
    descriptor: ()V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=1, locals=1, args_size=1
        start local 0 // com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS this
         0: .line 69
            aload 0 /* this */
            invokespecial java.lang.Object.<init>:()V
            return
        end local 0 // com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    1     0  this  Lcom/oracle/truffle/js/test/interop/TargetTypeMappingTest$ToBePassedToJS;

  public void json(com.oracle.truffle.js.test.interop.TargetTypeMappingTest$JsonObject);
    descriptor: (Lcom/oracle/truffle/js/test/interop/TargetTypeMappingTest$JsonObject;)V
    flags: (0x0001) ACC_PUBLIC
    Code:
      stack=2, locals=2, args_size=2
        start local 0 // com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS this
        start local 1 // com.oracle.truffle.js.test.interop.TargetTypeMappingTest$JsonObject c
         0: .line 74
            aload 0 /* this */
            aload 1 /* c */
            putfield com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS.jsonObject:Lcom/oracle/truffle/js/test/interop/TargetTypeMappingTest$JsonObject;
         1: .line 75
            return
        end local 1 // com.oracle.truffle.js.test.interop.TargetTypeMappingTest$JsonObject c
        end local 0 // com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS this
      LocalVariableTable:
        Start  End  Slot  Name  Signature
            0    2     0  this  Lcom/oracle/truffle/js/test/interop/TargetTypeMappingTest$ToBePassedToJS;
            0    2     1     c  Lcom/oracle/truffle/js/test/interop/TargetTypeMappingTest$JsonObject;
    RuntimeVisibleAnnotations: 
      org.graalvm.polyglot.HostAccess$Export()
    MethodParameters:
      Name  Flags
      c     
}
SourceFile: "TargetTypeMappingTest.java"
NestHost: com.oracle.truffle.js.test.interop.TargetTypeMappingTest
InnerClasses:
  public JsonObject = com.oracle.truffle.js.test.interop.TargetTypeMappingTest$JsonObject of com.oracle.truffle.js.test.interop.TargetTypeMappingTest
  public ToBePassedToJS = com.oracle.truffle.js.test.interop.TargetTypeMappingTest$ToBePassedToJS of com.oracle.truffle.js.test.interop.TargetTypeMappingTest
  public abstract Export = org.graalvm.polyglot.HostAccess$Export of org.graalvm.polyglot.HostAccess