code: public static String getActivityImplementor(String className) throws IOException {
          if (getActivityImplementors() != null) {
              String newImpl = getActivityImplementors().get(className);
              if (newImpl != null)
                  return newImpl;
          }
          return className;
      }
docs: If the className argument needs to be mapped to a new implementor class,
  returns the new class name; otherwise returns the unmodified argument.