input: Write a function to parse the given URL and print out the protocol, domain name, and path using Python.
  assert parse_url('https://www.example.com/path/to/file')==('https', 'www.example.com', '/path/to/file')
  assert parse_url('http://test.domain.com/subpath/file')==('http', 'test.domain.com', '/subpath/file')
  assert parse_url('ftp://user:pass@ftp.server.org/directory/file')==('ftp', 'user:pass@ftp.server.org', '/directory/file')
  assert parse_url('https://example.co.uk/')==('https', 'example.co.uk', '/')
  assert parse_url('http://localhost:8080/')==('http', 'localhost:8080', '/')
output: def parse_url(url):
      protocol_end = url.find('://')
      protocol = url[:protocol_end]
      remaining_url = url[protocol_end + 3:]
      domain_end = remaining_url.find('/')
      domain = remaining_url[:domain_end]
      path = remaining_url[domain_end:]
      return (protocol, domain, path)