Add some comments

Author: rerpha

forwarder/update_handlers/ca_update_handler.py

@@ -58,7 +58,12 @@ def __init__(
         (self._pv,) = context.get_pvs(
             pv_name, connection_state_callback=self._connection_state_callback
         )
+
+        # This is needed for the case when the PV doesn't exist before it has been added
+        # ie. if a gateway has not yet been configured.
+        # None means no timeout - it will eventually connect. 
         self._pv.timeout = None
+        
         # Subscribe with "data_type='time'" to get timestamp and alarm fields
         sub = self._pv.subscribe(data_type="time")
         sub.add_callback(self._monitor_callback)