code: def convert_merge(builder, layer, input_names, output_names, keras_layer):
      
      # Get input and output names
      output_name = output_names[0]
  
      mode = _get_elementwise_name_from_keras_layer(keras_layer)
      builder.add_elementwise(name = layer, input_names = input_names,
              output_name = output_name, mode = mode)
docs: Convert concat layer from keras to coreml.
  
      Parameters
      ----------
      keras_layer: layer
          A keras layer object.
  
      builder: NeuralNetworkBuilder
          A neural network builder object.