code: def convert_cropping(builder, layer, input_names, output_names, keras_layer):
      
      # Get input and output names
      input_name, output_name = (input_names[0], output_names[0])
  
      if isinstance(keras_layer, keras.layers.convolutional.Cropping1D):
          left, right = keras_layer.cropping
          top, bottom = (0, 0)
      else: # 2D
          left, right = keras_layer.cropping[0]
          top, bottom = keras_layer.cropping[1]
  
      # Now add the layer
      builder.add_crop(name = layer,
          left = left, right=right, top=top, bottom=bottom, offset = [0,0],
          input_names = [input_name], output_name=output_name
          )
docs: Convert padding layer from keras to coreml.
      Keras only supports zero padding at this time.
      Parameters
      ----------
      keras_layer: layer
          A keras layer object.
  
      builder: NeuralNetworkBuilder
          A neural network builder object.