The SOLUTION is to add the chapters you want as a epub.Link object. As an example:

epub.Link(chapter.file_name, chapter.title, chapter.id)
And add that result to a toc list object.

toc.append(link)
Then after you have added all the chapters / links you want, then you convert the list to a tuple.

toc = tuple(toc)
And set it as the book table of contents.

book.toc = toc

....book.spine.extend((addc,)) ???

.....
book = epub.read_epub(file_path)
addc = epub.EpubHtml(title='第二章', file_name='chapter_add.xhtml', lang='zh-CN')
addc.content = '

第二章

这是测试的第二章

'
# Add The Chapter To Object
book.add_item(addc)
book.spine.extend((addc,))
book.toc = (epub.Link('intro.xhtml', '简介', 'intro'),
(epub.Section('正文'),
(addc,))
://github.com/aerkalov/ebooklib.git)