code: def test_zero_loss(self):
      loss_func = NCALoss(10)
      for dtype in TEST_DTYPES:
          for embedding_angles, labels in [
              ([0, 20], [0, 0]),
              ([0], [0]),
          ]:
              embeddings = torch.tensor(
                  [angle_to_coord(a) for a in embedding_angles],
                  requires_grad=True,
                  dtype=dtype,
              ).to(
                  TEST_DEVICE
              )  # 2D embeddings
              labels = torch.LongTensor(labels)
              loss = loss_func(embeddings, labels)
              loss.backward()
              self.assertEqual(loss, 0)
  
file_path: pytorch-metric-learning/tests/losses/test_nca_loss.py
imports: import unittest
  import torch
  from pytorch_metric_learning.losses import NCALoss
  from ..None import TEST_DEVICE, TEST_DTYPES
  from ..zzz_testing_utils.testing_utils import angle_to_coord
label_desc: Use image node_id 2 for calling the TestNCALoss obj's underlying member method code with example usage: obj.test_zero_loss() without return types