Add default value

Author: brefra

plugwise/nodes/__init__.py

@@ -151,8 +151,8 @@ def rssi_out(self) -> int:
             return self._rssi_out
         return 0
 
-    def do_ping(self, callback):
-        """Send network ping message to node"""
+    def do_ping(self, callback=None):
+        """Send network ping message to node."""
         self._request_ping(callback, True)
 
     def _request_info(self, callback=None):