def _is_coin_small_and_unconfirmed(self, utxo: PartialTxInput) -> bool:
        """If true, the coin should not be spent.
        The idea here is that an attacker might send us a UTXO in a
        large low-fee unconfirmed tx that will ~never confirm. If we
        spend it as part of a tx ourselves, that too will not confirm
        (unless we use a high fee, but that might not be worth it for
        a small value UTXO).
        In particular, this test triggers for large "dusting transactions"
        that are used for advertising purposes by some entities.
        see #6960
        """
        # confirmed UTXOs are fine; check this first for performance:
        block_height = utxo.block_height
        assert block_height is not None
        if block_height > 0:
            return False
        # exempt large value UTXOs
        value_sats = utxo.value_sats()
        assert value_sats is not None
        threshold = self.config.WALLET_UNCONF_UTXO_FREEZE_THRESHOLD_SAT
        if value_sats >= threshold:
            return False
        # if funding tx has any is_mine input, then UTXO is fine
        funding_tx = self.db.get_transaction(utxo.prevout.txid.hex())
        if funding_tx is None:
            # we should typically have the funding tx available;
            # might not have it e.g. while not up_to_date
            return True
        if any(self.is_mine(self.adb.get_txin_address(txin))
               for txin in funding_tx.inputs()):
            return False
        return True
If true, the coin should not be spent.
        The idea here is that an attacker might send us a UTXO in a
        large low-fee unconfirmed tx that will ~never confirm. If we
        spend it as part of a tx ourselves, that too will not confirm
        (unless we use a high fee, but that might not be worth it for
        a small value UTXO).
        In particular, this test triggers for large "dusting transactions"
        that are used for advertising purposes by some entities.
        see #6960
        
electrum/wallet.py