title: Convert MobileNet from Keras to CoreML
body: <p>I'm using Keras 2.1.3 and I want to convert MobileNet to CoreML:</p>
  
  <pre><code>from keras.applications import MobileNet
  from keras.applications.mobilenet import relu6
  from keras.applications.mobilenet import DepthwiseConv2D
  
  import coremltools.converters.keras as k
  
  def save_model():
      model = MobileNet(input_shape=(128,128,3), include_top=False)
      model.save('temp.h5')
  
  def convert():
      model = k.convert('temp.h5',
                        input_names=['input'],
                        output_names=['output'],
                        model_precision='float16',
                        custom_conversion_functions={'relu6': relu6, 'DepthwiseConv2D': DepthwiseConv2D})
      model.save('temp.model')
  
  save_model()
  convert()
  </code></pre>
  
  <p>This gives an error: <code>ValueError: Unknown activation function:relu6</code></p>