updated docs

docs/LightningModule/RequiredTrainerInterface.md

@@ -57,6 +57,10 @@ class CoolModel(ptl.LightningModule):
         y_hat = self.forward(x)
         return {'val_loss': self.my_loss(y_hat, y)}
         
+    def validation_end(self, outputs):
+        avg_loss = torch.stack([x for x in outputs['val_loss']]).mean()
+        return avg_loss
+         
     def configure_optimizers(self):
         return [torch.optim.Adam(self.parameters(), lr=0.02)]