code: def test_l2_loss(self):
      pred = torch.Tensor([[1, 1, 0, 0, 0, 0, 1]])
      target = torch.Tensor([[1, 1, 0, 0, 0, 0, 0]])
  
      loss = L2Loss(
          neg_pos_ub=2,
          pos_margin=0,
          neg_margin=0.1,
          hard_mining=True,
          loss_weight=1.0,
      )
      assert torch.allclose(loss(pred, target), torch.tensor(0.1350))
  
imports: from unittest import TestCase
  import torch
  from mmdet.models import L2Loss
label_desc: Use image node_id 1 for calling the TestL2Loss obj's underlying member method code with example usage: obj.test_l2_loss() without return types