Allow passing an iterable with keys to subscribe to in EventHandlerBase.__init__()

lib/tfw/event_handler_base.py

@@ -3,6 +3,7 @@
 
 from abc import ABC, abstractmethod
 from inspect import currentframe
+from typing import Iterable
 
 from tfw.networking.event_handlers import ServerConnector
 from tfw.crypto import message_checksum, KeyManager, verify_message
@@ -20,7 +21,12 @@ class EventHandlerBase(ABC):
     """
     def __init__(self, key):
         self.server_connector = ServerConnector()
-        self.keys = [key]
+        self.keys = []
+        if isinstance(key, str):
+            self.keys.append(key)
+        elif isinstance(key, Iterable):
+            self.keys = list(key)
+
         self.subscribe(*self.keys)
         self.server_connector.register_callback(self.event_handler_callback)