input: Write a python function to convert HTML to plain text by removing HTML tags.
  assert html_to_text('<p>Hello, <b>world</b>!</p>') == 'Hello, world!'
  assert html_to_text('<div><a href="#">Link</a></div>') == 'Link'
  assert html_to_text('<span>Text with <br>line break</span>') == 'Text with line break'
output: def html_to_text(html):
      from html import unescape
      import re
  
      # Remove HTML tags using a regular expression
      text = re.sub('<[^<]+?>', '', html)
      # Unescape any HTML entities
      return unescape(text)