FunctionLibraryDefinition* library);

  // Write a copy of the input graph to 'graph_out', where the subgraphs are
  // replaced with calls to the new functions.
  Status BuildOutputGraph(Graph* graph_out, FunctionLibraryDefinition* library);

 private:
  // A subgraph of the input, all marked with a common 'group_attribute'
  // value.
  //