Added alias of "stopped"

Author: Joel Collins

src/labthings/actions/thread.py

@@ -138,9 +138,14 @@ def dead(self):
 
     @property
     def stopped(self):
-        """ """
+        """Has the thread been cancelled"""
         return self.stopping.is_set()
 
+    @property
+    def cancelled(self):
+        """Alias of `stopped`"""
+        return self.stopped
+
     def update_progress(self, progress: int):
         """
         Update the progress of the ActionThread.