Vel factory function

def create(input_width, input_height, input_channels=1, rnn_type='lstm', cnn_output_dim=512, hidden_units=128):
    """ Vel factory function """
    def instantiate(**_):
        return NatureCnnRnnBackbone(
            input_width=input_width, input_height=input_height, input_channels=input_channels,
            rnn_type=rnn_type, cnn_output_dim=cnn_output_dim, hidden_units=hidden_units
        )

    return ModelFactory.generic(instantiate)