diff --git a/core/modules/field/field.api.php b/core/modules/field/field.api.php
index d6bc578..e37afa3 100644
--- a/core/modules/field/field.api.php
+++ b/core/modules/field/field.api.php
@@ -300,3 +300,26 @@ function hook_field_purge_instance($instance) {
 /**
  * @} End of "addtogroup hooks".
  */
+
+/**
+ * Specifies the allowed values list for a field.
+ *
+ * @param FieldDefinitionInterface $field_definition
+ *   The field definition.
+ *
+ * @param EntityInterface $entity
+ *    The entity object.
+ *
+ * @return
+ *  An associative array to use with keys and values to use with the key|label
+ *  a field's allowed value list.
+ *
+ * @ingroup callbacks
+ */
+function callback_allowed_values_function(FieldDefinitionInterface $field_definition, EntityInterface $entity) {
+  $values = array(
+    0 => 'no',
+    1 => 'yes'
+  );
+  return $values;
+}