input: Write a python function to extract domain name from a given URL.
  assert extract_domain('http://www.zevera.com/somepath') == 'zevera.com'
  assert extract_domain('https://zevera.com/otherpath') == 'zevera.com'
  assert extract_domain('http://anotherdomain.org/page') == 'anotherdomain.org'
output: def extract_domain(url):
      from urllib.parse import urlparse
      parsed_url = urlparse(url)
      domain = parsed_url.netloc
      if domain.startswith('www.'):
          domain = domain[4:]
      return domain