piston changed pre event

src/main/java/me/km/events/CustomEventCaller.java

@@ -71,7 +71,7 @@ public class CustomEventCaller {
     }
 
     @SubscribeEvent
-    public void onPiston(PistonEvent e) {
+    public void onPiston(PistonEvent.Pre e) {
         if(e.getPistonMoveType() != PistonMoveType.EXTEND) {
             return;
         }