code: def validation_step(self, batch, batch_idx):
      log_dict = self._validation_step(batch, batch_idx)
      with self.ema_scope():
          log_dict_ema = self._validation_step(
              batch, batch_idx, suffix="_ema"
          )
      return log_dict
  
imports: import torch
  import pytorch_lightning
  import torch.nn.functional
  from contextlib import contextmanager
  from taming.modules.vqvae.quantize import VectorQuantizer2
  from ldm.modules.diffusionmodules.model import Encoder, Decoder
  from ldm.modules.distributions.distributions import DiagonalGaussianDistribution
  from ldm.util import instantiate_from_config
label_desc: Use image node_id 12 for calling the VQModel obj's underlying member method code with example usage: obj.validation_step(batch, batch_idx) and returns: log_dict