Hi there!
I was trying to fuzz your interesting library as part of my university testing task, when I encountered interesting detail - there is possibility to open debugger at runtime.
I used the following code:

parser = AdvancedHTMLParser.AdvancedHTMLParser()
parser.parseStr(html)
parser.getHTML()

I started fuzzing it. At some point of fuzzing I figured out that program just stopped. At first, I thought it was some infinite cycle case. However, after some research I realized that it was pdb activation which forced program to wait for key input. The following appeared in console:

> /lib/python3.9/site-packages/AdvancedHTMLParser/Tags.py(1531)innerHTML()
-> return ''.join(ret)
(Pdb)

I traced back to the place where pdb was opened and found the following code snippet (Tags.py:1530):

try:
 return ''.join(ret)
except:
 import pdb; pdb.set_trace()
 return ''.join(ret)

This happened when processing of the following input was underway: ",pMêom><`e<adbiT�L".
This case is quite rare, for sure. Although I recommend that you fix it.