input: Write a python function to extract hostname from a given URL.
  assert get_hostname("https://www.example.com/path/to/page") == "www.example.com"
  assert get_hostname("http://subdomain.example.co.uk/path") == "subdomain.example.co.uk"
  assert get_hostname("https://example.org") == "example.org"
output: def get_hostname(url):
      from urllib.parse import urlparse
      parsed_url = urlparse(url)
      return parsed_url.hostname