def _check_ongoing_submarine_swaps_callback(self) -> Optional[str]:
        """Callback that will return a warning string if there are unconfirmed swap funding txs."""
        from electrum.submarine_swaps import MIN_FINAL_CLTV_DELTA_FOR_CLIENT, LOCKTIME_DELTA_REFUND
        if not (self.wallet.has_lightning() and self.wallet.lnworker.swap_manager):
            return None
        if not self.network:
            return None
        ongoing_swaps = self.wallet.lnworker.swap_manager.get_pending_swaps()
        if not ongoing_swaps:
            return None
        is_forward = any(not swap.is_reverse for swap in ongoing_swaps)
        if is_forward:
            # fixme: this is inaccurate, we need local_height - cltv_of_htlc
            delta = MIN_FINAL_CLTV_DELTA_FOR_CLIENT
            warning = messages.MSG_FORWARD_SWAP_WARNING.format(delta)
        else:
            locktime = min(swap.locktime for swap in ongoing_swaps)
            delta = locktime - self.wallet.adb.get_local_height()
            warning = messages.MSG_REVERSE_SWAP_WARNING.format(delta)
        return "\n\n".join((
            _("Pending submarine swap"),
            warning,
        ))
Callback that will return a warning string if there are unconfirmed swap funding txs.
electrum/gui/qt/main_window.py