code: def get_license_from_url(url):
      
      if not url:
          return
  
      split_url = urlsplit(url, scheme='http')
  
      if split_url.netloc.lower() == 'creativecommons.org':
          if 'publicdomain' in split_url.path:
              match = _RE_PUBLIC_DOMAIN_URL.match(split_url.path)
              if match is None:
                  license = ['public domain']
              else:
                  license = ['CC0']
                  license.extend(part for part in match.groups() if part)
          else:
              license = ['CC']
              match = _RE_LICENSE_URL.match(split_url.path)
              license.extend(part.upper() for part in match.groups() if part)
      elif split_url.netloc == 'arxiv.org':
          license = ['arXiv']
          match = _RE_LICENSE_URL.match(split_url.path)
          license.extend(part for part in match.groups() if part)
      else:
          raise ValueError('Unknown license URL')
  
      return u' '.join(license)
docs: Get the license abbreviation from an URL.
  
      Args:
          url(str): canonical url of the license.
  
      Returns:
          str: the corresponding license abbreviation.
  
      Raises:
          ValueError: when the url is not recognized