code: boolean isValidPackageName(String s) {
          if (s.contains("/")) {
              String[] a = s.split("/");
              if (a.length == 2) {
                   return isValidPackageName0(a[0]) && isValidPackageName0(a[1]);
              }
              return false;
          }
          return isValidPackageName0(s);
      }
docs: Is the given string a valid package name?