code: function _updateEditorOverwriteMode(event) {
          var editor = EditorManager.getActiveEditor(),
              newstate = !editor._codeMirror.state.overwrite;
  
          // update label with no transition
          _updateOverwriteLabel(event, editor, newstate, true);
          editor.toggleOverwrite(newstate);
      }
docs: Update insert/overwrite indicator
  @param {Event} event (unused)