How do I programmatically render a custom entity? [closed]

Question

I created a custom entity (submenu) in Drupal 8. I need to render this custom entity in my custom module. This is the code I am using.

$entity_type = 'submenu';
$entity_id = '1'; // static for example purpose
$view_mode = 'full';         

$entity = \Drupal::entityTypeManager()->getStorage($entity_type)->load($entity_id);
$view_builder = \Drupal::entityTypeManager()->getViewBuilder('submenu');
$pre_render = $view_builder->view($entity, $view_mode);
$render_output = render($pre_render);

I keep getting the following error.

TypeError: Argument 1 passed to Drupal\Core\Entity\EntityViewBuilder::view() must implement interface Drupal\Core\Entity\EntityInterface, null given

Why do I get this error?

Answer 1

Make sure the entity id exists and the error disappears.