code: def _default_export_output(export_outputs, head_name):
      """Extracts the default export output from the given export_outputs dict."""
      if len(export_outputs) == 1:
          return next(six.itervalues(export_outputs))
      try:
          return export_outputs[_DEFAULT_SERVING_KEY]
      except KeyError:
          raise ValueError(
              "{} did not specify default export_outputs. "
              "Given: {} "
              "Suggested fix: Use one of the heads in tf.estimator, or include "
              "key {} in export_outputs.".format(
                  head_name, export_outputs, _DEFAULT_SERVING_KEY
              )
          )
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import abc
  import six
  import tensorflow
  from tensorflow import estimator
label_desc: Use image node_id 4 for calling a global function with example usage: _default_export_output(export_outputs, head_name) and returns: next, export_outputs