input: def clean_html_tags(str: str) -> str:
      """ Remove HTML tags from a given string.
      >>> clean_html_tags("<p>This is a <b>test</b> string</p>")
      'This is a test string'
      >>> clean_html_tags("<div>Hello <span>world</span></div>")
      'Hello world'
      """
      import re
      clean_str = re.sub("<.*?>", "", str)
      return clean_str
output:     import re
      clean_str = re.sub("<.*?>", "", str)
      return clean_str