class_docstr: LightningModule wrapper over WaveNet.
  
  Parameters
  ----------
  model_kwargs
      Keyword arguments to pass to WaveNet.
  lr, optional
      Learning rate, by default 1e-3
  weight_decay, optional
      Weight decay, by default 1e-8
class_docstr_tok: ["LightningModule","wrapper","over","WaveNet",".","Parameters","--","--","--","--","--","model_kwargs","Keyword","arguments","to","pass","to","WaveNet",".","lr",",","optional","Learning","rate",",","by","default","1e-3","weight_decay",",","optional","Weight","decay",",","by","default","1e-8"]
docstr: Execute validation step.
docstr_tok: ["Execute","validation","step","."]
code: def validation_step(self, batch, batch_idx: int):  # type: ignore
      """
      Execute validation step.
      """
      feat_static_cat = batch["feat_static_cat"]
      feat_static_real = batch["feat_static_real"]
      past_target = batch["past_target"]
      past_observed_values = batch["past_observed_values"]
      past_time_feat = batch["past_time_feat"]
      future_target = batch["future_target"]
      future_observed_values = batch["future_observed_values"]
      future_time_feat = batch["future_time_feat"]
      scale = batch["scale"]
  
      val_loss = self.model.loss(
          feat_static_cat=feat_static_cat,
          feat_static_real=feat_static_real,
          past_target=past_target,
          past_observed_values=past_observed_values,
          past_time_feat=past_time_feat,
          future_target=future_target,
          future_observed_values=future_observed_values,
          future_time_feat=future_time_feat,
          scale=scale,
      ).mean()
  
      self.log(
          "val_loss",
          val_loss,
          on_epoch=True,
          on_step=False,
          prog_bar=True,
      )
  
      return val_loss
  
file_path: gluonts/src/gluonts/torch/model/wavenet/lightning_module.py
imports: import lightning.pytorch
  import torch
  from gluonts.core.component import validated
  from .module import WaveNet
label_desc: Use image node_id 4 for calling the WaveNetLightningModule obj's underlying member method code with example usage: obj.validation_step(batch, batch_idx) and returns: val_loss