code: public List<JSTypeExpression> getExtendedInterfaces() {
      if (info == null || info.extendedInterfaces == null) {
        return ImmutableList.of();
      }
      return Collections.unmodifiableList(info.extendedInterfaces);
    }
docs: Returns the interfaces extended by an interface
  
  @return An immutable list of JSTypeExpression objects that can
  be resolved to types.