code: def test_tensor_train_on_batch_multi_output(self):
      x = torch.rand(ModelMultiOutputTest.batch_size, 1)
      y1 = torch.rand(ModelMultiOutputTest.batch_size, 1)
      y2 = torch.rand(ModelMultiOutputTest.batch_size, 1)
      loss = self.model.train_on_batch(x, (y1, y2))
      self.assertEqual(type(loss), float)
  
imports: import numpy
  import torch
  import torch.nn
  from torch.utils.data import DataLoader
  from poutyne import Model, TensorDataset
  from tests.framework.model.base import ModelFittingTestCase, MultiIOModel
label_desc: Use image node_id 4 for calling the ModelMultiOutputTest obj's underlying member method code with example usage: obj.test_tensor_train_on_batch_multi_output() without return types