input: Write a function to convert an HTML string to plain text without using any libraries. If the given HTML string is empty then return an empty string.
  assert html_to_text("<p>Hello, World!</p>")=='Hello, World!'
  assert html_to_text("<h1>Welcome</h1>")=='Welcome'
  assert html_to_text("<a href='example.com'>Link</a>")=='Link'
  assert html_to_text("<div><p>Paragraph</p></div>")=='Paragraph'
  assert html_to_text("")==''
output: def html_to_text(html):
      if not html:
          return ""
      text = ""
      inside_tag = False
      for char in html:
          if char == '<':
              inside_tag = True
          elif char == '>':
              inside_tag = False
          elif not inside_tag:
              text += char
      return text