code: public ClassDocImpl getClassDoc(ClassSymbol clazz) {
          ClassDocImpl result = classMap.get(clazz);
          if (result != null) return result;
          if (isAnnotationType(clazz)) {
              result = new AnnotationTypeDocImpl(this, clazz);
          } else {
              result = new ClassDocImpl(this, clazz);
          }
          classMap.put(clazz, result);
          return result;
      }
docs: Return the ClassDoc (or a subtype) of this class symbol.