code: def Graph(self):
      
      graph = graph_pb2.GraphDef()
      if self._graph is not None:
        graph.ParseFromString(self._graph)
        return graph
      raise ValueError('There is no graph in this EventAccumulator')
docs: Return the graph definition, if there is one.
  
      If the graph is stored directly, return that.  If no graph is stored
      directly but a metagraph is stored containing a graph, return that.
  
      Raises:
        ValueError: If there is no graph for this run.
  
      Returns:
        The `graph_def` proto.