src/yimaTheme/Theme/Theme.php
public function addChild(ModelInterface $child, $captureTo = null, $append = null)
    {
        parent::addChild($child, $captureTo, $append);

        if ($child instanceof ThemeDefaultInterface) {
            $child->parent = $this;
        }

        return $this;
    }
public function addChild(ModelInterface $child, $captureTo = null, $append = null)
    {
        parent::addChild($child, $captureTo, $append);

        if ($child instanceof ThemeDefaultInterface) {
            $child->parent = $this;
        }

        return $this;
    }
Add a child model

@param  ModelInterface $child
@param  null|string    $captureTo Optional; if specified, the "capture to" value to set on the child
@param  null|bool      $append    Optional; if specified, append to child  with the same capture

@return ViewModel