input: 
  import re
  
  # Clean a string of HTML tags 
  def clean_html_tags(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>This is a <span>test</span> string in a <p>paragraph</p></div>")
      'This is a test string in a paragraph'
      """
      clean_str = re.sub("<.*?>", "", str)
      return clean_str
  
output:     clean_str = re.sub("<.*?>", "", str)
      return clean_str