def rectified(model):
return backend.modify_model_backprop(model, '<STR_LIT>')<EOL>
Modifies backprop to only propagate positive gradients.

    Args:
        model: The `keras.models.Model` instance whose gradient computation needs to be overridden.

    References:
        Details can be found in the paper: [Visualizing and Understanding Convolutional Networks]
        (https://arxiv.org/pdf/1311.2901.pdf)