input: from typing import List
  
  def clean_html_tags(str: 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'
      >>> clean_html_tags("<div><span>Hello, World!</span></div>")
      'Hello, World!'
      """
output:     import re
      return re.sub(r'<[^>]+>', '', str)