class_docstr: A test for focal loss.
class_docstr_tok: ["A","test","for","focal","loss","."]
code: def test_sam(self):
      output0 = FocalLoss(gamma=0)(self.input, self.target)
      output1 = nn.NLLLoss2d()(F.log_softmax(self.input), self.target)
      self.assertGreaterEqual(1, abs(output0.item() - output1.item()))
  
file_path: towhee/tests/unittests/models/loss/test_focal_loss.py
imports: import unittest
  import random
  import torch
  import torch.nn.functional
  from torch.autograd import Variable
  from torch import nn
  from towhee.models.loss.focal_loss import FocalLoss
label_desc: Use image node_id 2 for calling the TestOperator obj's underlying member method code with example usage: obj.test_sam() without return types