code: def make_cache(self, backend=None):
          
          if backend is None:
              if self._default_backend is None:
                  backend = DEFAULT_BACKEND_NAME
              else:
                  backend = self._default_backend
          return self.__get_backend(backend).make_cache(self.ops, self.n_qubits)
docs: Make a cache to reduce the time of run. Some backends may implemented it.
  
          This is temporary API. It may changed or deprecated.