Prealoading added to ResponseIterator, some non-used code removed

src/ResponseIterator.php

@@ -2,10 +2,15 @@
 
 namespace RouterOS;
 
-use \Iterator,
-    \ArrayAccess,
-    \Countable,
-    \Serializable;
+use \Iterator;
+use \ArrayAccess;
+use \Countable;
+use \Serializable;
+use function array_keys;
+use function array_slice;
+use function count;
+use function serialize;
+use function unserialize;
 
 /**
  * This class was created by memory save reasons, it convert response
@@ -35,7 +40,7 @@ class ResponseIterator implements Iterator, ArrayAccess, Countable, Serializable
      *
      * @var array
      */
-    private $raw = [];
+    private $raw;
 
     /**
      * Initial value of array position