Vel factory function

def create(input_width, input_height, input_channels=1, output_dim=512):
    """ Vel factory function """
    def instantiate(**_):
        return NatureCnn(
            input_width=input_width, input_height=input_height, input_channels=input_channels,
            output_dim=output_dim
        )

    return ModelFactory.generic(instantiate)