code: def has_uncacheable_headers(self, response):
          
  
          cc_dict = get_header_dict(response, 'Cache-Control')
          if cc_dict:
              if 'max-age' in cc_dict and cc_dict['max-age'] == '0':
                  return True
              if 'no-cache' in cc_dict:
                  return True
              if 'private' in cc_dict:
                  return True
          if response.has_header('Expires'):
              if parse_http_date(response['Expires']) < time.time():
                  return True
          return False
docs: Should this response be cached based on it's headers
              broken out from should_cache for flexibility