diff --git a/xtendr/xtendrbase.py b/xtendr/xtendrbase.py
index d5c9234..21ee84d 100644
--- a/xtendr/xtendrbase.py
+++ b/xtendr/xtendrbase.py
@@ -23,3 +23,8 @@ class XtendRBase(ABC):
     @abstractmethod
     def stop(self):
         pass
+
+    @abstractmethod
+    def pre_load(self):
+        pass
+        
\ No newline at end of file