code: def get_pooler(self, pooler_name):
      if pooler_name == "bert_pooler":
          return BertPooler
      elif pooler_name == "identity":
          return nn.Identity
      elif hasattr(layers, pooler_name):
          return getattr(layers, pooler_name)
      else:
          raise NotImplementedError(
              f"{pooler_name} is not implemented."
          )
  
file_path: mmf/mmf/models/transformers/heads/mlp.py
imports: import copy
  from dataclasses import dataclass
  from typing import Dict, List, Optional
  import torch
  from mmf.common.registry import registry
  from mmf.models.transformers.base import BaseTransformerHead
  from mmf.modules import layers
  from omegaconf import OmegaConf, open_dict
  from torch import nn
label_desc: Use image node_id 3 for calling the MLP obj's underlying member method code with example usage: obj.get_pooler(pooler_name) and returns: BertPooler, nn, getattr