input: def clean_html_tags(str):
      """
      Remove all HTML tags from the input string.
      >>> clean_html_tags("<p>This is a <b>test</b> string</p>")
      'This is a test string'
      >>> clean_html_tags("<html><head><title>Sample</title></head><body>Content</body></html>")
      'SampleContent'
      """
      clean_str = re.sub("<.*?>", "", str)
      return clean_str
output:     
      import re
  