Python sphinx 警告：目录树包含对不存在文档的引用

我正在使用sphinx来记录我的Django应用程序

我有以下文档目录结构

docs
|- build
|- source
   |- _static
   |- _templates
   |- conf.py
   |- index.rst
   |- upgrade.rst
|- upgrade_changes
   |- migration
      |- index.rst
   |- index.rst
   |- library_changes.rst

而

docs/source/index.rst

的内容是

My App's documentation!
=============================================
App Description

Revamp Upgrade Changes
----------------------

.. toctree::
   :maxdepth: 2

   upgrade

source/upgrade.rst

文件包含

upgrade\u更改中的内容

.. include:: ../upgrade_changes/index.rst

而

/upgrade\u changes/index.rst

已经

Following is the list of all revamp related documentation.

.. toctree::
   :maxdepth: 2

   library_changes

我想为

library\u changes.rst

文件包含一个目录树，该文件与

index.rst

处于同一级别

但这是一个错误

upgrade_changes/index.rst:50: WARNING: toctree contains reference to nonexisting document 'library_changes'

如何将文件包含到同一级别的目录树中？