input: 
  def read_url(url: str) -> str:
      """ Given a URL, the function reads the content of the URL and returns it as a string. 
      If the URL is not accessible, the function returns None.
      
      Examples:
      >>> read_url('https://www.example.com')
      '<!doctype html>\n<html>\n<head>\n<title>Example Domain'
      >>> read_url('https://www.nonexistenturl12345.com')
      None
      """
  
output:     import requests
      try:
          response = requests.get(url)
          response.raise_for_status()
          return response.text
      except requests.RequestException:
          return None