fix test_detection. test=develop

python/paddle/fluid/tests/test_detection.py

@@ -484,7 +484,7 @@ class TestYoloDetection(unittest.TestCase):
         program = Program()
         with program_guard(program):
             x = layers.data(name='x', shape=[30, 7, 7], dtype='float32')
-            img_size = layers.data(name='x', shape=[2], dtype='int32')
+            img_size = layers.data(name='img_size', shape=[2], dtype='int32')
             boxes, scores = layers.yolo_box(x, img_size, [10, 13, 30, 13], 10,
                                             0.01, 32)
             self.assertIsNotNone(boxes)