Making unwrap public, because "Coding Standards"

src/Collection/CollectionInterface.php

@@ -855,5 +855,5 @@ interface CollectionInterface extends Iterator, JsonSerializable
      *
      * @return \Iterator
      */
-    public function _unwrap();
+    public function unwrap();
 }

src/Collection/CollectionTrait.php

@@ -544,7 +544,7 @@ trait CollectionTrait
      * {@inheritDoc}
      *
      */
-    public function _unwrap()
+    public function unwrap()
     {
         $iterator = $this;
         while (get_class($iterator) === 'Cake\Collection\Collection') {
@@ -552,4 +552,15 @@ trait CollectionTrait
         }
         return $iterator;
     }
+
+    /**
+     * Backwards compatible wrapper for unwrap()
+     *
+     * @return \Iterator
+     * @deprecated
+     */
+    public function _unwrap()
+    {
+        return $this->unwrap();
+    }
 }