code: def add_args(parser):
      TransformerModel.add_args(parser)
      # encoder head selection
      parser.add_argument(
          "--encoder-attn-head-select",
          action="store_true",
          default=False,
          help="encoder head selection",
      )
      parser.add_argument(
          "--total-encoder-attention-heads",
          type=int,
          help="total number of encoder attention heads",
      )
      # decoder self attention
      parser.add_argument(
          "--decoder-self-attn-head-select",
          action="store_true",
          default=False,
          help="decoder self-attention head selection",
      )
      # decoder-encoder attention
      parser.add_argument(
          "--dec-enc-attn-head-select",
          action="store_true",
          default=False,
          help="decoder-encoder attention head selection",
      )
      parser.add_argument(
          "--total-decoder-attention-heads",
          type=int,
          help="total number of decoder attention heads",
      )
      # selection strategy
      parser.add_argument(
          "--attn-head-select-strategy",
          type=str,
          help="attention head selection strategy, subset or group",
      )
  
imports: from typing import Any, List, Dict, Optional
  import torch
  import torch.nn
  from torch import Tensor
  from fairseq.utils import safe_hasattr
  from fairseq.models.transformer import TransformerModel, TransformerEncoder, TransformerDecoder
  from ..modules.attn_head_selector import AttnHeadSelector
  from ..modules.head_selection_transformer_layer import HeadSelectionTransformerEncoderLayer, HeadSelectionTransformerDecoderLayer
label_desc: Use image node_id 2 for calling the HeadSelectionTransformerModel obj's underlying member method code with example usage: obj.add_args(parser) without return types