code: def test_no_pos(self) -> None:
      pos_scores = torch.empty((0,), requires_grad=True)
      neg_scores = torch.empty((0, 3), requires_grad=True)
      loss_fn = RankingLossFunction(margin=1.0)
      loss = loss_fn(pos_scores, neg_scores, None)
      self.assertTensorEqual(loss, torch.zeros(()))
      loss.backward()
  
imports: from unittest import main, TestCase
  import torch
  from torchbiggraph.losses import LogisticLossFunction, RankingLossFunction, SoftmaxLossFunction
label_desc: Use image node_id 6 for calling the TestRankingLossFunction obj's underlying member method code with example usage: obj.test_no_pos() without return types