title: TensorFlow/Keras: How to get missing models (ResNet101, ResNeXt, etc.) from Keras' applications module?
body: <p>A number of documented <a href="https://keras.io/applications/" rel="nofollow noreferrer">Keras applications</a> are missing from my (up-to-date) Keras installation and TensorFlow 1.10 Keras API installation.
  I import Keras' applications module as suggested and use it as follows:</p>
  
  <pre><code>from keras import applications
  resnet = applications.ResNeXt101(include_top=False, weights='imagenet', input_shape=(SCALED_HEIGHT, SCALED_WIDTH, 3), pooling=None)
  </code></pre>
  
  <p>I also tried</p>
  
  <pre><code>resnet = applications.resnext.ResNeXt101(include_top=False, weights='imagenet', input_shape=(SCALED_HEIGHT, SCALED_WIDTH, 3), pooling=None)
  </code></pre>
  
  <p>But in both cases I get the same type of error:</p>
  
  <pre><code>AttributeError: module 'keras.applications' has no attribute 'ResNeXt101'
  </code></pre>
  
  <p>Printing <code>help(applications)</code> yields:</p>
  
  <pre><code>Help on package keras.applications in keras:
  
  NAME
      keras.applications
  
  PACKAGE CONTENTS
      densenet
      imagenet_utils
      inception_resnet_v2
      inception_v3
      mobilenet
      mobilenet_v2
      mobilenetv2
      nasnet
      resnet50
      vgg16
      vgg19
      xception
  
  FUNCTIONS
      DenseNet121 = wrapper(*args, **kwargs)
      DenseNet169 = wrapper(*args, **kwargs)
      DenseNet201 = wrapper(*args, **kwargs)
      InceptionResNetV2 = wrapper(*args, **kwargs)
      InceptionV3 = wrapper(*args, **kwargs)
      MobileNet = wrapper(*args, **kwargs)
      MobileNetV2 = wrapper(*args, **kwargs)
      NASNetLarge = wrapper(*args, **kwargs)
      NASNetMobile = wrapper(*args, **kwargs)
      ResNet50 = wrapper(*args, **kwargs)
      VGG16 = wrapper(*args, **kwargs)
      VGG19 = wrapper(*args, **kwargs)
      Xception = wrapper(*args, **kwargs)
      keras_modules_injection(base_fun)
  </code></pre>
  
  <p>which shows that the models initially aren't present in my installation. Why not? They're also not packaged in the TensorFlow's Keras API.</p>
  
  <p>I tried copying the files from the <a href="https://github.com/keras-team/keras-applications/tree/master/keras_applications" rel="nofollow noreferrer">Keras applications GitHub repository</a> and pasting them in <code>site-packages/keras/applications/</code>, but this results in the following stacktrace:</p>
  
  <pre><code>File "myscript.py", line 517, in get_fpn
      resnet = applications.resnext.ResNeXt101(include_top=False, weights='imagenet', input_shape=(SCALED_HEIGHT, SCALED_WIDTH, 3), pooling=None)
    File "site-packages/keras/applications/resnet_common.py", line 575, in ResNeXt101
      **kwargs)
    File "site-packages/keras/applications/resnet_common.py", line 348, in ResNet
      data_format=backend.image_data_format(),
  AttributeError: 'NoneType' object has no attribute 'image_data_format'
  </code></pre>
  
  <p>Any ideas on how to fix this? Why aren't these included and working in default installations of either Keras or TensorFlow? Why does the documentation not explain this?</p>