question: Getting Validation Accuracy with validation_epoch_end
context: Hello i managed to implement training accuracy per epoch with training_epoch_end but i want to do the same with validation accuracy with validation_epoch_end but i get an error of "too many indices for tensor of dimension 0" when train.fit() . I am using pytorch-lightning==1.2.8  . Thanks in advance.
  Error is:
  <ipython-input-31-41c968828bca> in validation_epoch_end(self, outputs)
       39     predictions = []
       40     for output in outputs:
  ---> 41       for out_labels in output["labels"].detach().cpu():
       42         labels.append(out_labels)
       43       for out_predictions in output["predictions"].detach().cpu():
  
  IndexError: too many indices for tensor of dimension 0
  
  def validation_step(self, batch, batch_idx):
     input_ids = batch["input_ids"]
     attention_mask = batch["attention_mask"]
     labels = batch["labels"]
     loss, outputs = self(input_ids, attention_mask, labels)
     self.log("val_loss", loss, prog_bar=True, logger=True)
     return loss
  
   def validation_epoch_end(self, outputs):
  
     labels = []
     predictions = []
     for output in outputs:
       for out_labels in output["labels"].detach().cpu():
         labels.append(out_labels)
       for out_predictions in output["predictions"].detach().cpu():
         predictions.append(out_predictions)
  
     labels = torch.stack(labels).int()
     predictions = torch.stack(predictions)
  
     validation_acc = accuracy(predictions, labels)
     self.logger.experiment.add_scalar("Validation Accuracy", validation_acc, self.current_epoch)
answer: I am a fool , i forgot to add return {"loss": loss, "predictions": outputs, "labels": labels} in the validation step.