diff --git a/core/modules/field/field.api.php b/core/modules/field/field.api.php
index 55c239d..56623b9 100644
--- a/core/modules/field/field.api.php
+++ b/core/modules/field/field.api.php
@@ -309,3 +309,30 @@ function hook_field_purge_field(\Drupal\field\Entity\FieldConfig $field) {
 /**
  * @} End of "addtogroup hooks".
  */
+
+/**
+ * Specifies the allowed values list for a field.
+ * 
+ * Callback for options_allowed_values().
+ *
+ * @param \Drupal\Core\Field\FieldDefinitionInterface $field_definition
+ *   The field definition.
+ * @param \Drupal\Core\Entity\EntityInterface $entity
+ *   The entity object.
+ * @param bool $cacheable
+ *   Specifies whether or not the allowed values will be statically cached.
+ *   Defaults to FALSE, set to TRUE to cache the values.
+ *
+ * @return array
+ *   An associative array with keys and values to use as the key|label setting(s)
+ *   on a field's allowed value list.
+ *
+ * @ingroup callbacks
+ */
+function callback_allowed_values(FieldDefinitionInterface $field_definition, EntityInterface $entity, &$cacheable = FALSE) {
+  $values = array(
+    0 => 'no',
+    1 => 'yes'
+  );
+  return $values;
+}
diff --git a/core/modules/options/options.module b/core/modules/options/options.module
index d221adb..f8db3cb 100644
--- a/core/modules/options/options.module
+++ b/core/modules/options/options.module
@@ -69,6 +69,11 @@ function options_field_storage_config_delete(FieldStorageConfigInterface $field_
  *
  * @see callback_allowed_values_function()
  */
+
+/**
+ * Implements callback_allowed_values().
+ *
+ */
 function options_allowed_values(FieldStorageDefinitionInterface $definition, FieldableEntityInterface $entity = NULL) {
   $allowed_values = &drupal_static(__FUNCTION__, array());