docstr: Build the transformer backend. Use the `BaseTransformerBackend` base class
  to inherit from when building a new backend. All the layers in the transformer
  backend model will be available (encoder, embeddings etc.) for use. Adjust
  your derived class based on the transformer backend you want to use.
docstr_tok: ["Build","the","transformer","backend",".","Use","the","`","BaseTransformerBackend","`","base","class","to","inherit","from","when","building","a","new","backend",".","All","the","layers","in","the","transformer","backend","model","will","be","available","(","encoder",",","embeddings","etc",".",")","for","use",".","Adjust","your","derived","class","based","on","the","transformer","backend","you","want","to","use","."]
code: def build_backend(self):
      """Build the transformer backend. Use the `BaseTransformerBackend` base class
      to inherit from when building a new backend. All the layers in the transformer
      backend model will be available (encoder, embeddings etc.) for use. Adjust
      your derived class based on the transformer backend you want to use.
      """
      backend_config = self.config.get("backend", {})
      backend_type = backend_config.get("type", "huggingface")
      backend_class = registry.get_transformer_backend_class(
          backend_type
      )
      self.backend = backend_class(self.config)
  
      if backend_config.get("freeze", False):
          for param in self.backend.parameters():
              param.requires_grad = False
  
imports: import logging
  from abc import ABC, abstractmethod
  from dataclasses import asdict, dataclass, field
  from typing import Any, Dict, List, NamedTuple, Optional, Tuple, Type
  from mmf.common.registry import registry
  from mmf.models import BaseModel
  from mmf.modules.encoders import IdentityEncoder
  from mmf.utils.modeling import get_bert_configured_parameters
  from omegaconf import MISSING, OmegaConf
  from torch import nn, Tensor
label_desc: Use image node_id 6 for calling the BaseTransformer obj's underlying member method code with example usage: obj.build_backend() without return types