GraphNode mouse-filter options

GraphNode seems to need the mouse-filter set to pass to work. If you try to set the mouse_filter (on GraphNode's _ready function or via the inspector), the mouse-filter gets reset. A workaround is to set the filter in the GraphNode's _gui_input event. But if you set the mouse-filter to STOP, you cannot drag and drop the GraphNode.
So it should be clear that you should not edit the mouse-filter and it should be clear why you shouldn't. Maybe with an example, how you can just filter some events. In my case, i just needed to filter the right-mouse-click events out, so i wrote this code in GraphNode:

```
func _on_GraphNode_gui_input(event):
if event is InputEventMouseButton and event.button_index == BUTTON_RIGHT and event.pressed:
self.mouse_filter = Control.MOUSE_FILTER_STOP
else:
self.mouse_filter = Control.MOUSE_FILTER_PASS
```