input: Write a function to remove all HTML tags from a given string. If there are no HTML tags, the function should return the original string unchanged. If the input string is empty, the function should return an empty string.
  def remove_html_tags(str):
      html_tag_pattern = re.compile(r'<[^>]+>')
      cleaned_str = re.sub(html_tag_pattern, '', str)
      return cleaned_str
  assert remove_html_tags("<p>This is a <b>test</b> string</p>") == "This is a test string"
  assert remove_html_tags("<h1>Title</h1><p>Content</p>") == "TitleContent"
  assert remove_html_tags("No HTML tags here") == "No HTML tags here"
  assert remove_html_tags("") == ""
  assert remove_html_tags("<p><br/></p>") == ""
output: def remove_html_tags(str):
      html_tag_pattern = re.compile(r'<[^>]+>')
      cleaned_str = re.sub(html_tag_pattern, '', str)
      return cleaned_str