fix

Author: vjik

src/Middleware/DataResponseMiddleware.php

@@ -4,6 +4,8 @@
 
 namespace Yiisoft\DataResponse\Middleware;
 
+use Yiisoft\DataResponse\DataStream\DataStream;
+
 /**
  * Middleware that applies a custom formatter to {@see DataStream} responses
  * and sets appropriate response headers.