input: Write a function to parse a given URL and print out the protocol, domain name, and path using Python. The function should use the `urllib.parse` module to extract these components and print them accordingly. If the URL is invalid or does not contain a protocol or domain name, the function should print appropriate messages.
  
  assert parse_url('https://www.example.com/path/to/file')==\
      'Protocol: https\nDomain name: www.example.com\nPath: /path/to/file'
  assert parse_url('http://example.net/some/path')==\
      'Protocol: http\nDomain name: example.net\nPath: /some/path'
  assert parse_url('ftp://user:password@example.org/directory')==\
      'Protocol: ftp\nDomain name: user:password@example.org\nPath: /directory'
  assert parse_url('invalid.url')==\
      'Invalid URL: Missing protocol or domain name'
  assert parse_url('')==\
      'Invalid URL: Empty string'
output: def parse_url(url):
      from urllib.parse import urlparse
      parsed_url = urlparse(url)
      if not parsed_url.scheme or not parsed_url.netloc:
          if not url:
              return 'Invalid URL: Empty string'
          return 'Invalid URL: Missing protocol or domain name'
      return f'Protocol: {parsed_url.scheme}\nDomain name: {parsed_url.netloc}\nPath: {parsed_url.path}'