Drupal 7: Strict warning: Only variables should be passed by.....

Drupal 7: Strict warning: Only variables should be passed by reference in
order_example_info_page() (line 33 of C:\xampp\htdocs\Drupal\
commerce_kickstart\sites\all\modules\commerce_examples\order_example\
order_example.module).
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Example block code:
function order_example_info_page() {
 $output = drupal_render(drupal_get_form('order_example_form'));
 return $output;
}
Change to:
function order_example_info_page() {
 $form = drupal_get_form('order_example_form');
 $output = drupal_render($form);
 return $output;
}
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