input: def clean_html_tags(html_string: str) -> str:
      """
      Remove all HTML tags from a given string.
      >>> clean_html_tags("<p>This is a <b>test</b> string</p>")
      'This is a test string'
      """
output:     
      import re
      return re.sub(r'<[^>]+>', '', html_string)
  