code: def get_serving_default_function(
      m: "tf_ext.Trackable",
  ) -> "tf_ext.ConcreteFunction":
      if not hasattr(m, "signatures"):
          raise EnvironmentError(
              f"{type(m)} is not a valid SavedModel format."
          )
      signatures: "tf_ext.SignatureMap" = getattr(m, "signatures")
      func = signatures.get(tf.compat.v2.saved_model.DEFAULT_SERVING_SIGNATURE_DEF_KEY)  # type: ignore
      if func is not None:
          return func
      raise BentoMLException(
          "Given Trackable objects doesn't contain a"
          " default functions from SignatureMap."
          " Most likely Tensorflow internal error."
      )
  
imports: from __future__ import annotations
  import importlib.metadata
  import importlib.util
  import logging
  import typing
  from typing import TYPE_CHECKING
  from bentoml.exceptions import BentoMLException
  from ...types import LazyType
  from ...utils.lazy_loader import LazyLoader
label_desc: Use image node_id 13 for calling a global function with example usage: get_serving_default_function(m) and returns: func