public function updateEditForm($form)
    {
        if ($this->isAssetAdmin() && $this->hasSecureAssets()) {
            
            if (($record = $form->getRecord()) && $record instanceof Folder) {
                
                if ($field = $form->Fields()->dataFieldByName('ViewerGroups')) {
                    
                    // Create Form Object:
                    
                    $dummy = Form::create(
                        $this->owner,
                        'EditForm',
                        FieldList::create(),
                        FieldList::create()
                    );
                    
                    // Populate Form Data:
                    
                    $dummy->loadDataFrom($record);
                    
                    // Define Form Action (allows ViewerGroups field to work in asset EditForm):
                    
                    $dummy->setFormAction(
                        sprintf(
                            '%s/field/File/item/%d/ItemEditForm',
                            $form->FormAction(),
                            $record->ID
                        )
                    );
                    
                    // Update Field Object:
                    
                    $field->setForm($dummy);
                    
                }
                
            }
            
        }
    }