code: def test_grid_head_loss(self, device):
      if device == "cuda":
          if not torch.cuda.is_available():
              return unittest.skip("test requires GPU and torch+cuda")
  
      grid_head = GridHead()
      grid_head.to(device=device)
  
      s = 256
      image_shapes = [(3, s, s)]
      batch_data_samples = demo_mm_inputs(
          batch_size=1,
          image_shapes=image_shapes,
          num_items=[1],
          num_classes=4,
          with_mask=True,
          device=device,
      )["data_samples"]
      proposals_list = demo_mm_proposals(
          image_shapes=image_shapes, num_proposals=100, device=device
      )
  
      train_cfg = ConfigDict(dict(pos_radius=1))
  
      # prepare ground truth
      (
          batch_gt_instances,
          batch_gt_instances_ignore,
          _,
      ) = unpack_gt_instances(batch_data_samples)
      sampling_results = demo_mm_sampling_results(
          proposals_list=proposals_list,
          batch_gt_instances=batch_gt_instances,
          batch_gt_instances_ignore=batch_gt_instances_ignore,
      )
  
      # prepare grid feats
      pos_bboxes = torch.cat(
          [res.pos_bboxes for res in sampling_results]
      )
      grid_feats = torch.rand((pos_bboxes.size(0), 256, 14, 14)).to(
          device
      )
      sample_idx = torch.arange(0, pos_bboxes.size(0))
      grid_pred = grid_head(grid_feats)
  
      grid_head.loss(grid_pred, sample_idx, sampling_results, train_cfg)
  
file_path: mmdetection/tests/test_models/test_roi_heads/test_mask_heads/test_grid_head.py
imports: import unittest
  from unittest import TestCase
  import torch
  from mmengine.config import ConfigDict
  from mmengine.structures import InstanceData
  from parameterized import parameterized
  from mmdet.models.roi_heads.mask_heads import GridHead
  from mmdet.models.utils import unpack_gt_instances
  from mmdet.testing import demo_mm_inputs, demo_mm_proposals, demo_mm_sampling_results
label_desc: Use image node_id 1 for calling the TestGridHead obj's underlying member method code with example usage: obj.test_grid_head_loss(device) and returns: unittest