class_docstr: Test the DDPOTrainer class.
class_docstr_tok: ["Test","the","DDPOTrainer","class","."]
code: def test_loss(self):
      advantage = torch.tensor([-1.0])
      clip_range = 0.0001
      ratio = torch.tensor([1.0])
      loss = self.trainer.loss(advantage, clip_range, ratio)
      self.assertEqual(loss.item(), 1.0)
  
file_path: trl/tests/test_ddpo_trainer.py
imports: import gc
  import unittest
  import torch
  from trl import is_diffusers_available, is_peft_available
  from .testing_utils import require_diffusers
label_desc: Use image node_id 3 for calling the DDPOTrainerTester obj's underlying member method code with example usage: obj.test_loss() without return types