input: def html_to_text(html_string: str) -> str:
      """ Converts a given HTML string to plain text by removing HTML tags.
      >>> html_to_text('<p>Hello, <strong>world</strong>!</p>')
      'Hello, world!'
      >>> html_to_text('This is a <a href="#">link</a>.')
      'This is a link.'
      """
output:     import re
      return re.sub(r'<[^>]+>', '', html_string)