code: def install_extensions() -> None:
      if not Doc.has_extension(DOC_EXT_ATTR):
          Doc.set_extension(DOC_EXT_ATTR, default=None)
  
imports: from typing import List, Callable, Iterable, Iterator, Optional, Dict, Union
  import warnings
  from spacy.language import Language
  from spacy.pipeline.trainable_pipe import TrainablePipe
  from spacy.pipeline.pipe import deserialize_config
  from spacy.tokens import Doc
  from spacy.vocab import Vocab
  from spacy.training import Example, validate_examples
  from spacy import util, Errors
  from spacy.util import minibatch
  from thinc.api import Model, Config, set_dropout_rate, Optimizer
  import srsly
  from pathlib import Path
  from .layers.transformer_model import huggingface_from_pretrained
  from .util import batch_by_length
  from .annotation_setters import null_annotation_setter
  from .data_classes import FullTransformerBatch, TransformerData
  from .layers import TransformerListener
label_desc: Use image node_id 2 for calling a global function with example usage: install_extensions() without return types