https://source.android.com/ 
public interface android.media.MediaMetadata2$TextKey extends java.lang.annotation.Annotation
  minor version: 0
  major version: 59
  flags: flags: (0x2601) ACC_PUBLIC, ACC_INTERFACE, ACC_ABSTRACT, ACC_ANNOTATION
  this_class: android.media.MediaMetadata2$TextKey
  super_class: java.lang.Object
{
}
SourceFile: "MediaMetadata2.java"
NestHost: android.media.MediaMetadata2
InnerClasses:
  public abstract TextKey = android.media.MediaMetadata2$TextKey of android.media.MediaMetadata2
    RuntimeVisibleAnnotations: 
      java.lang.annotation.Retention(value = java.lang.annotation.RetentionPolicy.SOURCE:Ljava/lang/annotation/RetentionPolicy;)