code: def _maybe_add_default_serving_output(export_outputs):
      """Add a default serving output to the export_outputs if not present.
  
      Args:
        export_outputs: Describes the output signatures to be exported to
          `SavedModel` and used during serving. Should be a dict.
  
      Returns:
        export_outputs dict with default serving signature added if necessary
  
      Raises:
        ValueError: if multiple export_outputs were provided without a default
          serving key.
      """
      if len(export_outputs) == 1:
          ((key, value),) = export_outputs.items()
          if (
              key
              != signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY
          ):
              export_outputs[
                  signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY
              ] = value
      if len(export_outputs) > 1:
          if (
              signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY
              not in export_outputs
          ):
              raise ValueError(
                  "Multiple export_outputs were provided, but none of them is "
                  "specified as the default.  Do this by naming one of them with "
                  "signature_constants.DEFAULT_SERVING_SIGNATURE_DEF_KEY."
              )
  
      return export_outputs
  
file_path: tensorflow/tensorflow/python/keras/saving/utils_v1/export_utils.py
imports: import collections
  import os
  import time
  from tensorflow.python.keras.saving.utils_v1 import export_output
  from tensorflow.python.keras.saving.utils_v1 import mode_keys
  from tensorflow.python.keras.saving.utils_v1 import unexported_constants
  from tensorflow.python.keras.saving.utils_v1.mode_keys import KerasModeKeys
  from tensorflow.python.platform import gfile
  from tensorflow.python.platform import tf_logging
  from tensorflow.python.saved_model import signature_constants
  from tensorflow.python.saved_model import signature_def_utils
  from tensorflow.python.saved_model import tag_constants
  from tensorflow.python.util import compat
label_desc: Use image node_id 7 for calling a global function with example usage: _maybe_add_default_serving_output(export_outputs) and returns: export_outputs