Embed meta data as a string constant in a TF graph.

  This function takes info, converts it into json, and embeds
  it in graph_def as a constant op called `__lucid_metadata_json`.

def infuse_metadata(graph_def, info):
  """Embed meta data as a string constant in a TF graph.

  This function takes info, converts it into json, and embeds
  it in graph_def as a constant op called `__lucid_metadata_json`.
  """
  temp_graph = tf.Graph()
  with temp_graph.as_default():
    tf.constant(json.dumps(info, cls=NumpyJSONEncoder), name=metadata_node_name)
  meta_node = temp_graph.as_graph_def().node[0]
  graph_def.node.extend([meta_node])