transport: fix typing after autoflake treatment

autoflake will remove all unused imports when `make style` is invoked,
but can't recognize typing names that are only used in comments.

this fixes it.

trezorlib/transport/__init__.py

@@ -16,10 +16,14 @@
 
 import importlib
 import logging
-from typing import Iterable, Type
+from typing import Iterable, List, Set, Type
 
 from ..protobuf import MessageType
 
+if False:
+    # mark Set and List as used, otherwise they only exist in comments
+    List, Set
+
 LOG = logging.getLogger(__name__)
 
 
@@ -106,7 +110,7 @@ def enumerate_devices() -> Iterable[Transport]:
     for transport in all_transports():
         name = transport.__name__
         try:
-            found = transport.enumerate()
+            found = list(transport.enumerate())
             LOG.info("Enumerating {}: found {} devices".format(name, len(found)))
             devices.extend(found)
         except NotImplementedError:

trezorlib/transport/bridge.py

@@ -17,13 +17,17 @@
 import logging
 import struct
 from io import BytesIO
-from typing import Any, Dict, Iterable
+from typing import Any, Dict, Iterable, Optional
 
 import requests
 
 from . import Transport, TransportException
 from .. import mapping, protobuf
 
+if False:
+    # mark Optional as used, otherwise it only exists in comments
+    Optional
+
 LOG = logging.getLogger(__name__)
 
 TREZORD_HOST = "http://127.0.0.1:21325"

trezorlib/transport/udp.py

@@ -15,11 +15,15 @@
 # If not, see <https://www.gnu.org/licenses/lgpl-3.0.html>.
 
 import socket
-from typing import Iterable, cast
+from typing import Iterable, Optional, cast
 
 from . import TransportException
 from .protocol import ProtocolBasedTransport, get_protocol
 
+if False:
+    # mark Optional as used, otherwise it only exists in comments
+    Optional
+
 
 class UdpTransport(ProtocolBasedTransport):
 

trezorlib/transport/webusb.py

@@ -17,13 +17,17 @@
 import atexit
 import sys
 import time
-from typing import Iterable
+from typing import Iterable, Optional
 
 import usb1
 
 from . import TransportException
 from .protocol import ProtocolBasedTransport, get_protocol
 
+if False:
+    # mark Optional as used, otherwise it only exists in comments
+    Optional
+
 DEV_TREZOR1 = (0x534C, 0x0001)
 DEV_TREZOR2 = (0x1209, 0x53C1)
 DEV_TREZOR2_BL = (0x1209, 0x53C0)