code: def clear_cache(self):
          
          for cmd in (self.cat_file_all, self.cat_file_header):
              if cmd:
                  cmd.__del__()
  
          self.cat_file_all = None
          self.cat_file_header = None
          return self
docs: Clear all kinds of internal caches to release resources.
  
          Currently persistent commands will be interrupted.
  
          :return: self