NameError: name 'content_image_features' is not defined

[masuta16]

---

NameError Traceback (most recent call last)
in ()
6 #combination_features = layer_features[2, :, :, :]
7
----> 8 loss += content_weight * content_loss(content_image_features,
9 combination_features)

NameError: name 'content_image_features' is not defined

I'm using python 3 and tensorflow 1.0.0