input: import requests
  
  def read_url(url):
    r = requests.get(url)
    if r.status_code == 200:
      return r.text
    else:
      return None
  
  ### Demonstrations:
  ##### Example 1:
  - Given URL: "https://www.example.com"
  - Expected Output: The HTML content of "https://www.example.com" or None if the request fails.
  
  ##### Example 2:
  - Given URL: "https://nonexistenturl.com"
  - Expected Output: None due to a failed request.
output:     if r.status_code == 200:
          return r.text
      else:
          return None