code: def create(input_width, input_height, input_channels=1, rnn_type='lstm', cnn_output_dim=512, hidden_units=128):
      
      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)
docs: Vel factory function