TF_CAPI_EXPORT extern TF_Operation* TF_GraphNextOperation(TF_Graph* graph,
                                                          size_t* pos);

// Write out a serialized representation of `graph` (as a GraphDef protocol
// message) to `output_graph_def` (allocated by TF_NewBuffer()).
// `output_graph_def`'s underlying buffer will be freed when TF_DeleteBuffer()
// is called.
//
// May fail on very large graphs in the future.