Untitled

function YOURTHEME_preprocess_page(array &$variables) {
    if (\Drupal::routeMatch()->getRouteName() == 'entity.node.canonical') {
        $node = \Drupal::routeMatch()->getParameter('node');
        if ($node instanceof \Drupal\node\NodeInterface && $node->bundle() == 'page') {
            $variables['hero_image'] = '';
            if ($node->hasField('field_hero_image') && !$node->get('field_hero_image')->isEmpty()) {
                $variables['hero_image'] = \Drupal::service('renderer')->render($node->get('field_hero_image')->view('hero_image'));
            }
        }
    }
}