docs: def _get_writer(self, i):
          """
          Returns a tuple of (log_fn, log_f, bin_fn, bin_f) to be written to by vectorized env channel i
          Or all Nones if recording is inactive on that channel
          """
          if self._recording_dir is None:
              return None
          if self._log_n is None:
              self._log_n = [None] * self.n
          if self._log_n[i] is None:
              self._log_n[i] = RecordingWriter(self._recording_dir, self._instance_id, i, async_write=self._async_write)
          return self._log_n[i]