https://www.graalvm.org/ 
interface com.oracle.truffle.api.instrumentation.test.SpecialService
  minor version: 0
  major version: 59
  flags: flags: (0x0600) ACC_INTERFACE, ACC_ABSTRACT
  this_class: com.oracle.truffle.api.instrumentation.test.SpecialService
  super_class: java.lang.Object
{
  public abstract java.lang.Object fileExtension();
    descriptor: ()Ljava/lang/Object;
    flags: (0x0401) ACC_PUBLIC, ACC_ABSTRACT
}
SourceFile: "SpecialService.java"