code: @Nonnull
      public BugInstance addSuperclass(PreorderVisitor visitor) {
          String className = ClassName.toDottedClassName(visitor.getSuperclassName());
          addClass(className);
          return this;
      }
docs: Add a class annotation for the superclass of the class the visitor is
  currently visiting.
  
  @param visitor
  the BetterVisitor
  @return this object