src/ORM/Hierarchy/MarkedSet.php
public function isTreeOpened(DataObject $node)
    {
        $id = $node->ID ?: 0;
        return !empty($this->treeOpened[$id]);
    }
public function isTreeOpened(DataObject $node)
    {
        $id = $node->ID ?: 0;
        return !empty($this->treeOpened[$id]);
    }
public function isTreeOpened ( DataObject $ node ) { $ id = $ node -> ID ? : 0 ; return ! empty ( $ this -> treeOpened [ $ id ] ) ; }
Check if this DataObject's tree is opened.
This is an expanded node which also should have children visually shown.

@param DataObject $node
@return bool
Check if this DataObject s tree is opened . This is an expanded node which also should have children visually shown .