code: def test_with_no_valid_pairs(self):
      alpha, beta, base = 0.1, 40, 0.5
      loss_func = MultiSimilarityLoss(alpha=alpha, beta=beta, base=base)
      for dtype in TEST_DTYPES:
          embedding_angles = [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([0])
          loss = loss_func(embeddings, labels)
          loss.backward()
          self.assertEqual(loss, 0)
  
file_path: pytorch-metric-learning/tests/losses/test_multi_similarity_loss.py
imports: import unittest
  import torch
  from pytorch_metric_learning.losses import MultiSimilarityLoss
  from ..None import TEST_DEVICE, TEST_DTYPES
  from ..zzz_testing_utils.testing_utils import angle_to_coord
  from .utils import get_pair_embeddings_with_ref
label_desc: Use image node_id 4 for calling the TestMultiSimilarityLoss obj's underlying member method code with example usage: obj.test_with_no_valid_pairs() without return types