code: def test_backend_op_config_set_qat_module(self):
      conf = BackendPatternConfig(torch.nn.Linear)
      self.assertTrue(conf.qat_module is None)
      conf.set_qat_module(nnqat.Linear)
      self.assertEqual(conf.qat_module, nnqat.Linear)
  
imports: import torch
  import torch.ao.nn.intrinsic
  import torch.ao.nn.qat
  import torch.ao.nn.quantized.reference
  from torch.testing._internal.common_quantization import QuantizationTestCase
  from torch.ao.quantization.backend_config import BackendConfig, BackendPatternConfig, DTypeConfig, DTypeWithConstraints, ObservationType
  from torch.ao.quantization.fuser_method_mappings import _sequential_wrapper2
  from torch.ao.quantization.fx.quantize_handler import _default_root_node_getter
label_desc: Use image node_id 11 for calling the TestBackendConfig obj's underlying member method code with example usage: obj.test_backend_op_config_set_qat_module() without return types