message: fix accidental typo on the added example densenet
diff: @@ -433,9 +433,9 @@ DOC = """
  ```python
  #Extract image features with DenseNet121
  - from keras.applications.DenseNet121 import DenseNet121
  + from keras.applications.densenet import DenseNet121
  from keras.preprocessing import image
  - from keras.applications.DenseNet121 import preprocess_input
  + from keras.applications.densenet import preprocess_input
  import numpy as np
  #create a DenseNet121 model pre-trained on imagenet
  