code: def _export_signatures(meta_graph):
      """Exports signatures from current graph into a MetaGraphDef."""
      named_signatures = tf.compat.v1.get_collection(
          _SIGNATURE_COLLECTION
      )
      if not named_signatures:
          raise ValueError(
              "No signatures present. Please call hub.add_signature(...)"
              "at least once in the module_fn."
          )
      for key, signature in named_signatures:
          meta_graph.signature_def[key].CopyFrom(signature)
  
imports: import collections
  import os
  import re
  from absl import logging
  import tensorflow
  from tensorflow_hub import module_attachment_pb2
  from tensorflow_hub import tf_utils
  from google.protobuf import message
  from tensorflow.core.protobuf import meta_graph_pb2
  from tensorflow.core.protobuf import saved_model_pb2
label_desc: Use image node_id 8 for calling a global function with example usage: _export_signatures(meta_graph) without return types