static const char* const kRetValOp = "_Retval";

class Encapsulator {
 public:
  Encapsulator(string group_attribute, Graph const* graph_in)
      : group_attribute_(std::move(group_attribute)), graph_in_(graph_in) {}

  // Find subgraphs marked with 'group_attribute', and build a new
  // subgraph, one for each value of 'group_attribute'.
  Status SplitIntoSubgraphs(FunctionLibraryDefinition* library);