code: def is_cache_valid(self):
          ''' Determines if the cache files have expired, or if it is still
          valid '''
  
          if os.path.isfile(self.cache_path_cache):
              mod_time = os.path.getmtime(self.cache_path_cache)
              current_time = time()
              if (mod_time + self.cache_max_age) > current_time:
                  if os.path.isfile(self.cache_path_index):
                      return True
  
          return Falsf is_cache_valid(self):
          ''' Determines if the cache files have expired, or if it is still
          valid '''
  
          if os.path.isfile(self.cache_path_cache):
              mod_time = os.path.getmtime(self.cache_path_cache)
              current_time = time()
              if (mod_time + self.cache_max_age) > current_time:
                  if os.path.isfile(self.cache_path_index):
                      return True
  
          return False
docs: Determines if the cache files have expired, or if it is still
          valid