qml: add some type hints to qetxfinalizer

diff --git a/electrum/gui/qml/qechannelopener.py b/electrum/gui/qml/qechannelopener.py
index 350c20e..927f7a8 100644
--- a/electrum/gui/qml/qechannelopener.py
+++ b/electrum/gui/qml/qechannelopener.py
@@ -15,6 +15,7 @@ from electrum.bitcoin import DummyAddress
 from electrum.lnworker import hardcoded_trampoline_nodes
 from electrum.logging import get_logger
 from electrum.fee_policy import FeePolicy
+from electrum.transaction import PartialTransaction
 
 from .auth import AuthMixin, auth_protect
 from .qetxfinalizer import QETxFinalizer
@@ -219,7 +220,7 @@ class QEChannelOpener(QObject, AuthMixin):
         self.finalizerChanged.emit()
 
     @auth_protect(message=_('Open Lightning channel?'))
-    def do_open_channel(self, funding_tx, conn_str, password):
+    def do_open_channel(self, funding_tx: PartialTransaction, conn_str, password):
         """
         conn_str: a connection string that extract_nodeid can parse, i.e. cannot be a trampoline name
         """
diff --git a/electrum/gui/qml/qetxfinalizer.py b/electrum/gui/qml/qetxfinalizer.py
index 368d0c6..2f74c7e 100644
--- a/electrum/gui/qml/qetxfinalizer.py
+++ b/electrum/gui/qml/qetxfinalizer.py
@@ -2,7 +2,7 @@ import copy
 from enum import IntEnum
 import threading
 from decimal import Decimal
-from typing import Optional, TYPE_CHECKING
+from typing import Optional, TYPE_CHECKING, Callable
 from functools import partial
 
 from PyQt6.QtCore import pyqtProperty, pyqtSignal, pyqtSlot, QObject, pyqtEnum
@@ -55,7 +55,7 @@ class FeeSlider(QObject):
         self._wallet = None  # type: Optional[QEWallet]
         self._sliderSteps = 0
         self._sliderPos = 0
-        self._fee_policy = None
+        self._fee_policy = None  # type: Optional[FeePolicy]
         self._target = ''
         self._config = None  # type: Optional[SimpleConfig]
 
@@ -150,7 +150,7 @@ class TxFeeSlider(FeeSlider):
         self._fee = QEAmount()
         self._feeRate = ''
         self._rbf = False
-        self._tx = None
+        self._tx = None  # type: Optional[PartialTransaction]
         self._inputs = []
         self._outputs = []
         self._finalized_txid = ''
@@ -244,7 +244,7 @@ class TxFeeSlider(FeeSlider):
     def doUpdate(self):
         self.update()
 
-    def update_from_tx(self, tx):
+    def update_from_tx(self, tx: PartialTransaction):
         tx_size = tx.estimated_size()
         fee = tx.get_fee()
         feerate = Decimal(fee) / tx_size  # sat/byte
@@ -256,7 +256,7 @@ class TxFeeSlider(FeeSlider):
         self.update_inputs_from_tx(tx)
         self.update_outputs_from_tx(tx)
 
-    def update_inputs_from_tx(self, tx):
+    def update_inputs_from_tx(self, tx: Transaction):
         inputs = []
         for inp in tx.inputs():
             # addr = self.wallet.adb.get_txin_address(txin)
@@ -277,7 +277,7 @@ class TxFeeSlider(FeeSlider):
             })
         self.inputs = inputs
 
-    def update_outputs_from_tx(self, tx):
+    def update_outputs_from_tx(self, tx: PartialTransaction):
         sm = self._wallet.wallet.lnworker.swap_manager if self._wallet.wallet.lnworker else None
 
         outputs = []
@@ -315,7 +315,13 @@ class QETxFinalizer(TxFeeSlider):
     finished = pyqtSignal([bool, bool, bool], arguments=['signed', 'saved', 'complete'])
     signError = pyqtSignal([str], arguments=['message'])
 
-    def __init__(self, parent=None, *, make_tx=None, accept=None):
+    def __init__(
+        self,
+        parent=None,
+        *,
+        make_tx: Callable[[int, FeePolicy], PartialTransaction] = None,
+        accept: Callable[[PartialTransaction], None] = None,
+    ):
         super().__init__(parent)
         self.f_make_tx = make_tx
         self.f_accept = accept
diff --git a/electrum/gui/qml/qewallet.py b/electrum/gui/qml/qewallet.py
index 8a4d6a6..b9c593d 100644
--- a/electrum/gui/qml/qewallet.py
+++ b/electrum/gui/qml/qewallet.py
@@ -637,14 +637,14 @@ class QEWallet(AuthMixin, QObject, QtEventListener):
 
         # TODO: properly catch server side errors, e.g. bad-txns-inputs-missingorspent
 
-    def save_tx(self, tx: 'PartialTransaction'):
+    def save_tx(self, tx: 'PartialTransaction') -> bool:
         assert tx
 
         try:
             if not self.wallet.adb.add_transaction(tx):
                 self.saveTxError.emit(tx.txid(), 'conflict',
                             _("Transaction could not be saved.") + "\n" + _("It conflicts with current history."))
-                return
+                return False
             self.wallet.save_db()
             self.saveTxSuccess.emit(tx.txid())
             self.historyModel.initModel(True)