refresh(changedTiddlers) {

    // TiddlyMap never needs a full refresh so we return false
    return false;

  }
This function is called by the system to notify the widget about
tiddler changes. It is ignored by TiddlyMap.

ATTENTION: TiddlyMap doesn't use the refresh mechanism here.
The caretaker module dispatches an `updates` object that provides
more advanced information, tailored to the needs of TiddlyMap.
These updates are picked up by {@link MapWidget#update}.

@override