can remove config from a metaconfig

tiramisu/api.py

@@ -1002,6 +1002,10 @@ class TiramisuContextConfig(TiramisuContext):
                persistent=False):
         return Config(self.config_bag.context.new_config(session_id=session_id, persistent=persistent))
 
+    def _m_pop(self,
+               session_id):
+        return Config(self.config_bag.context.pop_config(session_id=session_id))
+
     def _m_list(self):
         return self._g_list()
 

tiramisu/config.py

@@ -1140,3 +1140,10 @@ class KernelMetaConfig(KernelGroupConfig):
         config._impl_meta = weakref.ref(self)
         self._impl_children.append(config)
         return config
+
+    def pop_config(self,
+                   session_id):
+        for idx, child in enumerate(self._impl_children):  # pragma: no cover
+            if session_id == child._impl_name:
+                return self._impl_children.pop(idx)
+        raise ConfigError(_('cannot find the config {}').format(session_id))