At first glance, I think it's natural to think that `.next_sibling` and `previous_sibling` should be siblings tags. But it resulted in NavigableString like `"\n"` when I played with it today.

After carefully checking [its documentation](https://www.crummy.com/software/BeautifulSoup/bs4/doc/), it has noted that:

```
In real documents, the .next_sibling or .previous_sibling of a tag will usually be a string containing whitespace. Going back to the “three sisters” document:

<a href="http://example.com/elsie" class="sister" id="link1">Elsie</a>
<a href="http://example.com/lacie" class="sister" id="link2">Lacie</a>
<a href="http://example.com/tillie" class="sister" id="link3">Tillie</a>
You might think that the .next_sibling of the first <a> tag would be the second <a> tag. But actually, it’s a string: the comma and newline that separate the first <a> tag from the second:

link = soup.a
link
# <a class="sister" href="http://example.com/elsie" id="link1">Elsie</a>

link.next_sibling
# u',\n'
The second <a> tag is actually the .next_sibling of the comma:

link.next_sibling.next_sibling
# <a class="sister" href="http://example.com/lacie" id="link2">Lacie</a>

```

Why is that?