code: def test_solov2_head_empty_result(self):
      s = 256
      img_metas = {
          "img_shape": (s, s, 3),
          "ori_shape": (s, s, 3),
          "scale_factor": 1,
          "batch_input_shape": (s, s, 3),
      }
  
      mask_feature_head = _fake_mask_feature_head()
      mask_head = SOLOV2Head(
          num_classes=4,
          in_channels=1,
          mask_feature_head=mask_feature_head,
      )
  
      kernel_preds = torch.empty(0, 128)
      cls_scores = torch.empty(0, 80)
      mask_feats = torch.empty(0, 16, 16)
      test_cfg = ConfigDict(
          score_thr=0.1,
          mask_thr=0.5,
      )
      results = mask_head._predict_by_feat_single(
          kernel_preds=kernel_preds,
          cls_scores=cls_scores,
          mask_feats=mask_feats,
          img_meta=img_metas,
          cfg=test_cfg,
      )
  
      self.assertIsInstance(results, InstanceData)
      self.assertEqual(len(results), 0)
  
file_path: mmdetection/tests/test_models/test_dense_heads/test_solov2_head.py
imports: from unittest import TestCase
  import numpy
  import torch
  from mmengine.config import ConfigDict
  from mmengine.structures import InstanceData
  from mmdet import *
  from mmdet.models.dense_heads import SOLOV2Head
  from mmdet.structures.mask import BitmapMasks
label_desc: Use image node_id 2 for calling the TestSOLOv2Head obj's underlying member method code with example usage: obj.test_solov2_head_empty_result() without return types