code: def to_proto(spec):
      """Encodes a nested spec into a struct_pb2.StructuredValue proto.
  
      Args:
        spec: Nested list/tuple or dict of TensorSpecs, describing the shape of the
          non-batched Tensors.
  
      Returns:
        A `struct_pb2.StructuredValue` proto.
      """
      # Make sure spec is a tensor_spec.
      spec = from_spec(spec)
      return nested_structure_coder.encode_structure(spec)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import os
  from typing import Union
  import numpy
  import tensorflow
  import tensorflow_probability
  from tf_agents.specs import array_spec
  from tf_agents.typing import types
  from google.protobuf import text_format
  from tensorflow.core.protobuf import struct_pb2
  from tensorflow.python.framework import tensor_spec
  from tensorflow.python.saved_model import nested_structure_coder
label_desc: Use image node_id 18 for calling a global function with example usage: to_proto(spec) and returns: nested_structure_coder