input: Write a function to parse the given URL and print out the protocol, domain name, and path using Python. The function should use the `urllib.parse` library to parse the URL and extract the required components. If the given URL is empty, the function should print out a message indicating that the URL is empty. 
  
  def parse_url(url):
      if not url:
          print("The URL is empty.")
          return
      
      parsed_url = urllib.parse.urlparse(url)
      
      protocol = parsed_url.scheme
      domain_name = parsed_url.netloc
      path = parsed_url.path
      
      print('Protocol:', protocol)
      print('Domain name:', domain_name)
      print('Path:', path)
  
  assert parse_url('https://www.example.com/path/to/file')==None # Should print "Protocol: https", "Domain name: www.example.com", "Path: /path/to/file"
  assert parse_url('http://test.com/abc')==None # Should print "Protocol: http", "Domain name: test.com", "Path: /abc"
  assert parse_url('')==None # Should print "The URL is empty."
  assert parse_url('ftp://example.org/dir/file')==None # Should print "Protocol: ftp", "Domain name: example.org", "Path: /dir/file"
  assert parse_url('https://www.google.com/')==None # Should print "Protocol: https", "Domain name: www.google.com", "Path: /"
output: def parse_url(url):
      if not url:
          print("The URL is empty.")
          return
      
      parsed_url = urllib.parse.urlparse(url)
      
      protocol = parsed_url.scheme
      domain_name = parsed_url.netloc
      path = parsed_url.path
      
      print('Protocol:', protocol)
      print('Domain name:', domain_name)
      print('Path:', path)