Better handling html <ruby> tags

Sorry for my English.Please let me know if there are somethings that I'm not making clear.

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/ruby

The tag is often found in Japanese ebooks.

html='<p>ある<ruby>日<rp>（</rp><rt>ひ</rt><rp>）</rp></ruby>の<ruby>放課<rp>（</rp><rt>ほうか</rt><rp>）</rp>後<rp>（</rp><rt>ご</rt><rp>）</rp></ruby>だった。</p>'

from bs4 import BeautifulSoup
soup = BeautifulSoup(html,'lxml')
soup.get_text()

'ある日（ひ）の放課（ほうか）後（ご）だった。'.

We may not need the part in parentheses, but the string is still readable though.

But in case that the fall-back <rp> tag is omitted by the ebook publisher:

html='<p>ある<ruby>日<rt>ひ</rt></ruby>の<ruby>放課<rt>ほうか</rt>後<rt>ご</rt></ruby>だった。</p>'
soup = BeautifulSoup(html,'lxml')
soup.get_text()

'ある日ひの放課ほうか後ごだった。'

This one is quite confusing,since Kanji and it's hiragana(pronunciation) repeat twice but having the same meaning.

Yes, the string in <rp> and <rt> could be ignored by get_text() in an undocumented way I found in bs4's element.py and test.py:

from bs4 import BeautifulSoup
from bs4.element import NavigableString, Script, Stylesheet, TemplateString, Tag

class RTString(NavigableString):
    '''class for <rt> tag'''
    pass

class RPString(NavigableString):
    '''class for <rp> tag'''
    pass

string_containers = {
    'rp': RPString,
    'rt': RTString,
    'style': Stylesheet,
    'script': Script,
    'template': TemplateString,
}

html='<p>ある<ruby>日<rp>（</rp><rt>ひ</rt><rp>）</rp></ruby>の<ruby>放課<rp>（</rp><rt>ほうか</rt><rp>）</rp>後<rp>（</rp><rt>ご</rt><rp>）</rp></ruby>だった。</p>'
soup = BeautifulSoup(html,'lxml'string_containers =string_containers)
soup.get_text()

'ある日の放課後だった。'

soup.get_text(types={NavigableString,RTString,RPString,})

'ある日（ひ）の放課（ほうか）後（ご）だった。'

But could Beautifully Soup handle <rp> and <rt> tag internally like <script> rather than end user implement?
And also a little hint in the documentation?
I think these tags are standard html tags,not user custom tags.Many East Asian languages also use these tags, such as Pinyin in Chinese.

OS windows 10
beautifulsoup4==4.9.3
lxml==4.6.3