Fix for get method and get_str method implemented

devices.py

             loc (numeric): Location (see LOC_* in props)
             roo (numeric): Room (see ROO_* in props)
             fun (numeric): Function (see FUN_* in props)
-            num (numeric): Device number in case of multiple devices
         """
-        topic = self.__topic__(stg, loc, roo, fun)
+        topic = topic_by_props(stg, loc, roo, fun)
         return self[topic]
 
+    def get_str(self, stg, loc, roo, fun):
+        """Method to get a device by str version of props
+
+        Args:
+            stg (str): Source transmittion group (see SIS_* in props)
+            loc (str): Location (see LOC_* in props)
+            roo (str): Room (see ROO_* in props)
+            fun (str): Function (see FUN_* in props)
+        """
+        return self.get(getattr(props, stg), getattr(props, loc), getattr(props, roo), getattr(props, fun))
+
 
 class physical_devices(base):
     """