code: public ClassDoc exception() {
          ClassDocImpl exceptionClass;
          if (!(holder instanceof ExecutableMemberDoc)) {
              exceptionClass = null;
          } else {
              ExecutableMemberDocImpl emd = (ExecutableMemberDocImpl)holder;
              ClassDocImpl con = (ClassDocImpl)emd.containingClass();
              exceptionClass = (ClassDocImpl)con.findClass(exceptionName);
          }
          return exceptionClass;
      }
docs: Return the exception as a ClassDocImpl.