code: def __call__(self, sample):
      if dataset_keys.VALID_MASK_IMG in sample:
          valid_mask = sample[dataset_keys.VALID_MASK_IMG]
      else:
          valid_mask = sample[dataset_keys.HIGH_RES_DEPTH_IMG] != 0
      if self.gt_low_limit is not None:
          valid_mask = valid_mask & (
              sample[dataset_keys.HIGH_RES_DEPTH_IMG]
              > self.gt_low_limit
          )
      if self.gt_high_limit is not None:
          valid_mask = valid_mask & (
              sample[dataset_keys.HIGH_RES_DEPTH_IMG]
              < self.gt_high_limit
          )
      sample[dataset_keys.VALID_MASK_IMG] = valid_mask
      return sample
  
imports: import dataset_keys
label_desc: Use image node_id 2 for calling the ValidDepthMask obj's underlying member method code with example usage: obj.__call__(sample) and returns: sample