input: def parse_url(url: str):
      """Parses the given URL and prints out the protocol, domain name, and path.
      Example:
      >>> parse_url('https://www.example.com/path/to/file')
      Protocol: https
      Domain name: www.example.com
      Path: /path/to/file
      """
output:     protocol_end = url.find('://')
      if protocol_end != -1:
          protocol = url[:protocol_end]
          url = url[protocol_end + 3:]
      else:
          protocol = None
  
      domain_end = url.find('/')
      if domain_end != -1:
          domain = url[:domain_end]
          path = url[domain_end:]
      else:
          domain = url
          path = None
  
      print(f"Protocol: {protocol}")
      print(f"Domain name: {domain}")
      print(f"Path: {path}")