code: public AnnotationVisitor visitAnnotation(String name, String desc) {
          if (av != null) {
              return av.visitAnnotation(name, desc);
          }
          return null;
      }
docs: Visits a nested annotation value of the annotation.
  
  @param name
  the value name.
  @param desc
  the class descriptor of the nested annotation class.
  @return a visitor to visit the actual nested annotation value, or
  <tt>null</tt> if this visitor is not interested in visiting this
  nested annotation. <i>The nested annotation value must be fully
  visited before calling other methods on this annotation
  visitor</i>.