input: def html_to_text(html_string):
      """Converts a given HTML string to plain text by removing all HTML tags.
      
      >>> html_to_text('<p>Hello, <b>world</b>!</p>')
      'Hello, world!'
      >>> html_to_text('<a href="example.com">Link</a>')
      'Link'
      >>> html_to_text('<div>This is a <span>test</span>.</div>')
      'This is a test.'
      """
      output = ''
      in_tag = False
      for char in html_string:
          if char == '<':
              in_tag = True
          elif char == '>':
              in_tag = False
          elif not in_tag:
              output += char
      return output
output:     output = ''
      in_tag = False
      for char in html_string:
          if char == '<':
              in_tag = True
          elif char == '>':
              in_tag = False
          elif not in_tag:
              output += char
      return output