input: from typing import Callable
  
  def clean_html_tags(input_str: str, cleaner: Callable[[str], str]) -> str:
      """Clean a string of HTML tags using a provided cleaning function.
      >>> clean_html_tags("<p>This is a <b>test</b> string</p>", re.compile("<.*?>").sub)
      'This is a test string'
      """
      return cleaner("", input_str)
output:     return cleaner(input_str, "")