code: def test_with_no_valid_triplets(self):
      loss_func = HistogramLoss(n_bins=4)
      for dtype in TEST_DTYPES:
          embeddings = torch.randn(
              5,
              32,
              requires_grad=True,
              dtype=dtype,
          ).to(TEST_DEVICE)
          labels = torch.LongTensor([0, 1, 2, 3, 4])
          loss = loss_func(embeddings, labels)
          self.assertEqual(loss, 0)
          loss.backward()
  
file_path: pytorch-metric-learning/tests/losses/test_histogram_loss.py
imports: import unittest
  import torch
  from numpy.testing import assert_almost_equal
  from pytorch_metric_learning.losses import HistogramLoss
  from pytorch_metric_learning.utils import common_functions
  from ..None import TEST_DEVICE, TEST_DTYPES
label_desc: Use image node_id 2 for calling the TestHistogramLoss obj's underlying member method code with example usage: obj.test_with_no_valid_triplets() without return types