Updated documentation to reflect the actual behavoir of the code.

islandora.api.php

@@ -638,7 +638,8 @@ function hook_CMODEL_PID_islandora_overview_object_alter(AbstractObject &$object
  *     module_name_derivative_creation_function($object, $force = FALSE)
  *     These functions must return an array in the structure of:
  *     - success: Bool denoting whether the operation was successful.
- *     - messages: An array structure containing:
+ *     - messages: An array structure containing zero or more array's with the
+ *       following fields:
  *       - message: A string passed through t() describing the
  *         outcome of the operation.
  *       - message_sub: (Optional) Substitutions to be passed along to t() or
@@ -704,7 +705,7 @@ function hook_CMODEL_PID_islandora_derivative() {
 function hook_islandora_update_related_objects_properties(AbstractObject $object) {
   $related_objects = get_all_children_siblings_and_friends($object);
   $pids_to_return = array();
-  foreach($related_objects as $related_object) {
+  foreach ($related_objects as $related_object) {
     $pids_to_return[] = $related_object->id;
   }
   return $pids_to_return;