code: def learn(self, obs, label):
      cost = self.alg.learn(obs, label)
  
imports: import numpy
  import unittest
  import os
  import torch
  import torch.nn
  import torch.optim
  import parl
label_desc: Use image node_id 2 for calling the TestAgent obj's underlying member method code with example usage: obj.learn(obs, label) without return types