to_pil_image changes (#762)

Author: surgan12

torchvision/transforms/functional.py

@@ -117,7 +117,7 @@ def to_pil_image(pic, mode=None):
 
         elif pic.ndimension() == 2:
             # if 2D image, add channel dimension (CHW)
-            pic.unsqueeze_(0)
+            pic = pic.unsqueeze(0)
 
     elif isinstance(pic, np.ndarray):
         if pic.ndim not in {2, 3}: