input: Write a function to convert an HTML string to plain text without using any libraries. The function should remove all HTML tags and return the text content.
  
  def html_to_text(html_string):
      output = ''
      in_tag = False
      for char in html_string:
          if char == '<':
              in_tag = True
          elif char == '>':
              in_tag = False
          elif in_tag == False:
              output += char
      return output
  
  assert html_to_text("<p>Hello, <b>world</b>!</p>")=="Hello, world!"
  assert html_to_text("<div><span>Text</span> here</div>")=="Text here"
  assert html_to_text("") == ""
  assert html_to_text("No tags here") == "No tags here"
  assert html_to_text("<a href='#'>Link</a>") == "Link"
output: def html_to_text(html_string):
      output = ''
      in_tag = False
      for char in html_string:
          if char == '<':
              in_tag = True
          elif char == '>':
              in_tag = False
          elif in_tag == False:
              output += char
      return output