input: Write a function to parse a given URL and return its protocol, domain name, and path as a tuple in Python. If the URL is invalid or cannot be parsed, return None.
  
  
  import urllib.parse
  
  def parse_url(url):
      try:
          parsed_url = urllib.parse.urlparse(url)
          protocol = parsed_url.scheme
          domain_name = parsed_url.netloc
          path = parsed_url.path
          return (protocol, domain_name, path)
      except ValueError:
          return None
  
  **Test Cases:**
  
  
  assert parse_url('https://www.example.com/path/to/file') == ('https', 'www.example.com', '/path/to/file')
  assert parse_url('http://example.org') == ('http', 'example.org', '/')
  assert parse_url('ftp://user:password@ftp.example.com') == ('ftp', 'user:password@ftp.example.com', '/')
  assert parse_url('invalid_url') == None
  assert parse_url('') == None
  
output: import urllib.parse
  
  def parse_url(url):
      try:
          parsed_url = urllib.parse.urlparse(url)
          protocol = parsed_url.scheme
          domain_name = parsed_url.netloc
          path = parsed_url.path
          return (protocol, domain_name, path)
      except ValueError:
          return None