code: def add_head(self, model, name, **kwargs):
      model.add_masked_lm_head(name)
      return self.default_input_samples_shape[-1]
  
imports: import unittest
  from datasets import load_dataset
  from transformers import AutoTokenizer, BertGenerationConfig
  from transformers.testing_utils import require_torch
  from .composition.test_parallel import ParallelAdapterInferenceTestMixin, ParallelTrainingMixin
  from .methods import BottleneckAdapterTestMixin, CompacterTestMixin, IA3TestMixin, LoRATestMixin, PrefixTuningTestMixin, PromptTuningTestMixin, UniPELTTestMixin
  from .test_adapter import AdapterTestBase, make_config
  from .test_adapter_backward_compability import CompabilityTestMixin
  from .test_adapter_conversion import ModelClassConversionTestMixin
  from .test_adapter_embeddings import EmbeddingTestMixin
  from .test_adapter_fusion_common import AdapterFusionModelTestMixin
  from .test_adapter_heads import PredictionHeadModelTestMixin
label_desc: Use image node_id 1 for calling the BertGenerationAdapterTestBase obj's underlying member method code with example usage: obj.add_head(model, name) and returns: self