input: from typing import List
  
  def html_to_text(html_string: str) -> str:
      """ Converts an HTML string to plain text by removing HTML tags.
      >>> html_to_text("<p>Hello, <b>world</b>!</p>")
      'Hello, world!'
      >>> html_to_text("<div><h1>Title</h1><p>This is a paragraph.</p></div>")
      'TitleThis is a paragraph.'
      >>> html_to_text("<a href='example.com'>Link</a>")
      'Link'
      """
output:     import re
      text = re.sub(r'<[^>]+>', '', html_string)
      return text