function my_module_field_info() { return array( 'my_custom_field' => array( 'label' => t('My Custom Field'), 'description' => t('A custom field for user profiles.'), 'settings' => array( 'display' => array( 'label' => t('Display Settings'), 'description' => t('Choose how to display this field on user profiles.'), 'type' => 'select', 'options' => array( 'above' => t('Above the user info'), 'below' => t('Below the user info'), 'none' => t('Do not display'), ), ), ), 'instance_settings' => array( 'default_value' => 'default', ), 'field_types' => array('text'), ), ); }This example demonstrates the use of a module to create a custom field for user profiles on a Drupal site. The code uses an array to define the properties of the field, such as its label, description, and display settings. In terms of package libraries, Drupal is built using a number of different PHP libraries, including Symfony, Guzzle, and PHPUnit. These libraries provide functionality for things like routing, HTTP requests, and testing.