code: def test_step(self, batch, batch_idx):
      # save image
      images, depths = self._shared_predict(batch)
      self.test_images.append(images)
      self.test_depths.append(depths)
  
imports: import os
  import random
  import cv2
  import imageio
  import numpy
  import torch
  from nemo.collections.multimodal.models.nerf.txt2nerf_base import Txt2NerfBase
  from nemo.collections.multimodal.modules.nerf.loss.laplacian_smooth_loss import LaplacianSmoothLoss
  from nemo.collections.multimodal.modules.nerf.loss.normal_consistency_loss import NormalConsistencyLoss
  from nemo.collections.multimodal.modules.nerf.materials.materials_base import ShadingEnum
  from nemo.core import optim
label_desc: Use image node_id 4 for calling the DreamFusion obj's underlying member method code with example usage: obj.test_step(batch, batch_idx) without return types