def get_mpp_amounts(self, payment_key: bytes) -> Optional[Tuple[int, int]]:
        """Returns (total received amount, expected amount) or None."""
        mpp_status = self.received_mpp_htlcs.get(payment_key.hex())
        if not mpp_status:
            return None
        total = sum([_htlc.amount_msat for scid, _htlc in mpp_status.htlc_set])
        return total, mpp_status.expected_msat
Returns (total received amount, expected amount) or None.
electrum/lnworker.py