remove superflous to-str

Signed-off-by: Tim van Katwijk <[email protected]>

Author: tim-vk

dockerfile_parse/parser.py

@@ -356,7 +356,7 @@ def parent_images(self):
                 in_stage = True
                 image, _ = image_from(instr['value'])
                 if image is not None:
-                    image = WordSplitter(image.to_str(), args=top_args).dequote()
+                    image = WordSplitter(image, args=top_args).dequote()
                     parents.append(image)
         return parents