code: def test_supervised_training_step(self):
      self.trainer.training_step(self.batch, 0)
      self.trainer.on_train_epoch_end()
  
file_path: ReAgent/reagent/test/training/cb/test_supervised_trainer.py
imports: import unittest
  import torch
  from reagent.core.types import CBInput
  from reagent.gym.policies.policy import Policy
  from reagent.gym.policies.samplers.discrete_sampler import GreedyActionSampler
  from reagent.models.cb_fully_connected_network import CBFullyConnectedNetwork
  from reagent.training.cb.supervised_trainer import SupervisedTrainer
  from reagent.training.parameters import SupervisedTrainerParameters
label_desc: Use image node_id 2 for calling the TestSupervisedTrainer obj's underlying member method code with example usage: obj.test_supervised_training_step() without return types