code: def test_foreground(self):
      background = torch.ones(1, 1, 5, 5)
      foreground = torch.zeros(1, 1, 5, 5)
      target = torch.cat((background, foreground), dim=1)
      input = torch.cat((background, foreground), dim=1)
      target[:, 0, 2, 2] = 0
      target[:, 1, 2, 2] = 1
  
      fgbg = FocalLoss(to_onehot_y=False, include_background=True)(
          input, target
      )
      fg = FocalLoss(to_onehot_y=False, include_background=False)(
          input, target
      )
      self.assertAlmostEqual(float(fgbg.cpu()), 0.1116, places=3)
      self.assertAlmostEqual(float(fg.cpu()), 0.1733, places=3)
  
imports: from __future__ import annotations
  import unittest
  import numpy
  import torch
  import torch.nn
  import torch.nn.functional
  from parameterized import parameterized
  from monai.losses import FocalLoss
  from monai.networks import one_hot
  from tests.utils import test_script_save
label_desc: Use image node_id 11 for calling the TestFocalLoss obj's underlying member method code with example usage: obj.test_foreground() without return types