input: Write a function to convert a given HTML string to plain text without using any libraries. The function should remove all HTML tags and return the plain 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><p>This is a test</p></div>")=="This is a test"
  assert html_to_text("<a href='example.com'>Link</a>")=="Link"
  assert html_to_text("No tags here")=="No tags here"
  assert html_to_text("")==""
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