ConfigurableObject: add set_default() / set_defaults() methods

mylib/config.py

@@ -1156,6 +1156,16 @@ class ConfigurableObject:
 
         return default if default is not None else self._defaults.get(option)
 
+    def set_default(self, option, default_value):
+        """Set option default value"""
+        assert option in self._defaults, f"Unkown option {option}"
+        self._defaults[option] = default_value
+
+    def set_defaults(self, **default_values):
+        """Set options default value"""
+        for option, default_value in default_values.items():
+            self.set_default(option, default_value)
+
     def configure(self, comment=None, **kwargs):
         """Configure options on registered mylib.Config object"""
         assert self._config, (