code: def convert_padding(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.ZeroPadding1D):
          left, right = keras_layer.padding
          top, bottom = (0, 0)
      else: # 2D
          top, left = keras_layer.padding
          bottom, right = keras_layer.padding
  
      # Now add the layer
      builder.add_padding(name = layer,
          left = left, right=right, top=top, bottom=bottom, value = 0,
          input_name = 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.