Fixed error: Call to private method in entity_usage_form_alter().

entity_usage.module

@@ -6,6 +6,7 @@
  */
 
 use Drupal\Core\Cache\CacheableMetadata;
+use Drupal\Core\Entity\EntityFormInterface;
 use Drupal\Core\Entity\EntityInterface;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Routing\RouteMatchInterface;
@@ -85,7 +86,7 @@ function entity_usage_field_storage_config_delete(FieldStorageConfigInterface $f
  */
 function entity_usage_form_alter(&$form, FormStateInterface $form_state, $form_id) {
   $form_object = $form_state->getFormObject();
-  if (!method_exists($form_object, 'getEntity')) {
+  if (!$form_object instanceof EntityFormInterface) {
     return;
   }
   /** @var \Drupal\Core\Entity\EntityInterface $entity */
@@ -107,7 +108,7 @@ function entity_usage_form_alter(&$form, FormStateInterface $form_state, $form_i
   if (!in_array($entity_type_id, $edit_entity_types) && !in_array($entity_type_id, $delete_entity_types)) {
     return;
   }
-  $is_edit_form = method_exists($form_object, 'getOperation') && $form_object->getOperation() === 'edit' && in_array($entity_type_id, $edit_entity_types);
+  $is_edit_form = $form_object->getOperation() === 'edit' && in_array($entity_type_id, $edit_entity_types);
   $is_delete_form = FALSE;
   if (!$is_edit_form && in_array($entity_type_id, $delete_entity_types)) {
     // Even if this is not on the UI, sites can define additional form classes