code: def clean_url(url, force_scheme=None):
      
      # URL should be ASCII according to RFC 3986
      url = str(url)
      # Collapse ../../ and related
      url_parts = urlparse.urlparse(url)
      path_parts = []
      for part in url_parts.path.split('/'):
          if part == '.':
              continue
          elif part == '..':
              if path_parts:
                  path_parts.pop()
          else:
              path_parts.append(part)
  
      url_parts = list(url_parts)
      if force_scheme:
          url_parts[0] = force_scheme
      url_parts[2] = '/'.join(path_parts)
  
      if FLAGS.keep_query_string == False:
          url_parts[4] = ''    # No query string
  
      url_parts[5] = ''    # No path
  
      # Always have a trailing slash
      if not url_parts[2]:
          url_parts[2] = '/'
  
      return urlparse.urlunparse(url_parts)
docs: Cleans the given URL.