private void log(String msg) {
    if (processingEnv.getOptions().containsKey("debug")) {
      processingEnv.getMessager().printMessage(Kind.NOTE, msg);
    }
  }
Returns the contents of a {@code Class[]}-typed "value" field in a given {@code
annotationMirror}.
service/processor/src/main/java/com/google/auto/service/processor/AutoServiceProcessor.java